Polymeric michelle composition with improved stability

ABSTRACT

Polymeric compositions capable of forming stable micelles in an aqueous solution, comprising an amphiphilic block copolymer of a hydrophilic block and a hydrophobic block, and a polylactic acid derivative wherein one end of the polylactic acid is covalently bound to at least one carboxyl group. The carboxyl group of the polylactic acid derivative may be fixed with a di- or tri-valent metal ion, obtained by adding the di- or tri-valent metal ion to the polymeric composition.

[0001] This application claims benefit of a patent application filedearlier as PCT International Application No. PCT/KR02/01942, filed onOct. 17, 2002, which claims priority to Korean Application No.2001/76213, filed on Dec. 4, 2001, and Korean Application No.2001/64468, filed on Oct. 18, 2001.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a polymeric micelle composition,and more specifically, to a polymeric micelle composition comprising anamphiphilic block copolymer composed of a hydrophilic block and ahydrophobic block, and a polylactic acid derivative having at least oneterminal carboxyl group.

[0004] 2. Related Art

[0005] Recently, nanoparticle and polymeric micelle systems usingbiodegradable polymers have been reported to be extremely usefultechnologies which can alter the in vivo distribution of anintravenously administered drug thereby reducing its side effects andimproving its efficacy. These systems offer advantages such as specificcell targeting and control of the release of the drug. They also havegood compatibility with body fluids and improve the solubility andbioavailability of poorly water-soluble drugs.

[0006] A method for preparing block copolymer micelles by physicallyentrapping a drug in the block copolymer which is composed of ahydrophilic component and a hydrophobic component was disclosed in EP 0583,955A2, and JP 206,815/94. The block copolymer employed is an A-Btype diblock copolymer comprising a polyethylene oxide as thehydrophilic A component and a polyamino acid or derivatives thereofhaving a hydrophobic functional group as the hydrophobic B component.Polymeric micelles comprising the above block copolymer can physicallyincorporate a drug, e.g. adriamycin, indomethacin, etc. into the innercore of the polymeric micelles, which can then be used as a drugdelivery carrier. However, these polymeric micelles are comprised ofblock copolymers that cannot be readily degraded in vivo. In addition,the b lock copolymers have poor biocompatibility, which can causeundesirable side effects when administered in vivo.

[0007] Great effort has been devoted to the development of abiodegradable and biocompatible core-shell type drug carrier withimproved stability and efficacy, and which will entrap a poorlywater-soluble drug. A method for preparation of chemically fixedpolymeric micelles, wherein the polymer is a core-shell type polymercomprising a hydrophilic polyethylene oxide as the shell and ahydrophobic biodegradable polymer that is cross-linked in an aqueoussolution as the core, was disclosed in EP 0,552,802A2. However, thispolymeric micelle is difficult to prepare because crosslinkers must beintroduced into the hydrophobic component of the A-B type diblock orA-B-A type triblock copolymer so that the core-forming polymer has astable structure. Also, administering a crosslinker that has never beenused in the human body leads to safety concerns.

[0008] On the other hand, in order to solubilize a hydrophobic drug,there has been reported a polymeric micelle composed of a di- ortri-block copolymer comprising a hydrophilic polymer of polyalkyleneglycol derivatives and a hydrophobic biodegradable polymer such as fattyacid polyesters or polyamino acids. U.S. Pat. No. 5,449,513 discloses adiblock copolymer comprising polyethylene glycol as the hydrophilicpolymer, and a polyamino acid derivative, e.g. polybenzyl aspartic acid,etc. as the hydrophobic polymer. This diblock copolymer can solubilizehydrophobic anticancer agents, e.g. doxorubicin, or anti-inflammatoryagents, e.g. indomethacin. However, the polyamino acid derivativescannot be hydrolyzed in vivo, and thus cause side effects due to immuneresponses.

[0009] U.S. Pat. No. 5,429,826 discloses a di- or multi-block copolymercomprising a hydrophilic polyalkylene glycol and a hydrophobicpolylactic acid. Specifically, the above patent describes a method ofstabilizing polymeric micelles by micellizing a di- or multi-blockcopolymer wherein an acrylic acid derivative is bonded to a terminalgroup of the di- or multi-block copolymer in an aqueous solution, whichthen crosslinks the polymers in order to form the micelles. The abovemethod could accomplish stabilization of the polymeric micelle, but thecrosslinked polymer is not degraded, and thus, cannot be applied for invivo use. The above polymeric micelles can solubilize a large amount ofa poorly water-soluble drug in an aqueous solution with a neutral pH,but have the drawback that they release the drug within a short periodof time.

[0010] In view of the foregoing, development of an improved polymericmicelle composition for hydrophobic drug delivery that is biocompatibleand biodegradable will be appreciated and desired. Thus, the presentinvention provides such an improved polymeric micelle composition whichis biocompatible and biodegradable and which can effectively deliver ahydrophobic drug without a decrease in its stability.

SUMMARY OF THE INVENTION

[0011] The present invention relates to a polymeric micelle compositioncomprising an amphiphilic block copolymer and a polylactic acidderivative containing at least one carboxyl terminal group. The presentinvention also relates to a polymeric composition wherein the carboxylterminal group of the polylactic acid derivative is fixed with a di- ortri-valent metal ion. The compositions of the present invention can formstable polymeric micelles or nanoparticles in body fluids or aqueoussolutions. The micelles or nanoparticles formed from the compositions ofthe present invention have a hydrophilic outer shell and a hydrophobicinner core wherein a large amount of hydrophobic drug can be physicallytrapped. The drug containing micelles and nanoparticles of the presentinvention have a prolonged retention time in the bloodstream afteradministration, and can be utilized to make various pharmaceuticalformulations. Additional features and advantages of the invention willbe apparent from the detailed description that follows, which when takenin conjunction with the accompanying drawings together illustrate, byway of example, features of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 is a schematic diagram of a polymeric micelle formed bymonomethoxypolyethylene glycol-polylactide (mPEG-PLA) in an aqueousenvironment.

[0013]FIG. 2 is a schematic diagram of a polymeric micelle formed bysodium carboxylate derivatized D,L-polylactic acid in an aqueousenvironment.

[0014]FIG. 3 is a schematic diagram of a polymeric micelle formed by amixture of monomethoxypolyethylene glycol-polylactide (mPEG-PLA) andsodium carboxylate derivatized D,L-polylactic acid in an aqueousenvironment.

[0015]FIG. 4 is a schematic diagram of a Ca²⁺-fixed polymeric micelle ofFIG. 3.

[0016]FIG. 5 is a schematic diagram of a Ca²⁺-fixed polymeric micellecontaining a hydrophobic drug trapped within the hydrophobic core of themicelle.

[0017]FIG. 6 is a graph showing the plasma drug concentration of adrug-containing Ca²⁺-fixed polymeric micelle at various time intervalsafter administration.

[0018]FIG. 7 illustrates the plasma concentration profiles of Ca²⁺-fixedpolymeric micelles, Cremophor EL and Tween 80 preparations,respectively.

[0019]FIG. 8a shows the anticancer effects of drug containing Ca²⁺-fixedpolymeric micelles in mice using the human prostatic carcinoma cell linePPC-1.

[0020]FIG. 8b shows the anticancer effects of drug containing Ca²⁺-fixedpolymeric micelles in mice using the human colon cancer cell line HT-29.

DETAILED DESCRIPTION OF THE INVENTION

[0021] Before the present polymeric compositions and methods of usingand making thereof are disclosed and described, it is to be understoodthat this invention is not limited to the particular configurations,process steps, and materials disclosed herein as such configurations,process steps, and materials may vary somewhat. It is also to beunderstood that the terminology employed herein is used for the purposeof describing particular embodiments only and is not intended to belimiting since the scope of the present invention will be limited onlyby the appended claims and equivalents thereof.

[0022] It must be noted that, as used in this specification and theappended claims, the singular forms “a,” “an,” and “the” include pluralreferents unless the context clearly dictates otherwise. Thus, forexample, reference to a polymer containing “a terminal group” includesreference to two or more such groups, and reference to “a hydrophobicdrug” includes reference to two or more of such drugs.

[0023] In describing and claiming the present invention, the followingterminology will be used in accordance with the definitions set outbelow.

[0024] As used herein, the term “bioactive agent” or “drug” or any othersimilar term means any chemical or biological material or compoundsuitable for administration by methods previously known in the artand/or by the methods taught in the present invention and that induce adesired biological or pharmacological effect. Such effects may includebut are not limited to (1) having a prophylactic effect on the organismand preventing an undesired biological effect such as preventing aninfection, (2) alleviating a condition caused by a disease, for example,alleviating pain or inflammation caused as a result of disease, and/or(3) either alleviating, reducing, or completely eliminating a diseasefrom the organism. The effect may be local, such as providing for alocal anesthetic effect, or it may be systemic.

[0025] As used herein, the term “biodegradable” or “biodegradation” isdefined as the conversion of materials into less complex intermediatesor end products by solubilization hydrolysis, or by the action ofbiologically formed entities which can be enzymes or other products ofthe organism.

[0026] As used herein, the term “biocompatible” means materials or theintermediates or end products of materials formed by solubilizationhydrolysis, or by the action of biologically formed entities which canbe enzymes or other products of the organism and which cause no adverseeffects on the body.

[0027] “Poly(lactide)” or “PLA” shall mean a polymer derived from thecondensation of lactic acid or by the ring opening polymerization oflactide. The terms “lactide” and “lactate” are used interchangeably.

[0028] As used herein, “effective amount” means the amount of abioactive agent that is sufficient to provide the desired local orsystemic effect and performance at a reasonable risk/benefit ratio aswould attend any medical treatment.

[0029] As used herein, “administering” and similar terms meansdelivering the composition to the individual being treated such that thecomposition is capable of being circulated systemically. Preferably, thecompositions of the present invention are administered by thesubcutaneous, intramuscular, transdermal, oral, transmucosal,intravenous, or intraperitoneal routes. Injectables for such use can beprepared in conventional forms, either as a liquid solution orsuspension, or in a solid form that is suitable for preparation as asolution or suspension in a liquid prior to injection, or as anemulsion. Suitable excipients that can be used for a dministrationinclude, for example, water, saline, dextrose, glycerol, ethanol, andthe like; and if desired, minor amounts of auxiliary substances such aswetting or emulsifying agents, buffers, and the like can be used. Fororal administration, it can be formulated into various forms such assolutions, tablets, capsules, etc.

[0030] Reference will now be made to the exemplary embodiments andspecific language will be used herein to describe the same. It willnevertheless be understood that no limitation of the scope of theinvention is thereby intended. Alterations and further modifications ofthe inventive features illustrated herein, and additional applicationsof the principles of the invention as illustrated herein, which wouldoccur to one skilled in the relevant art and having possession of thisdisclosure, are to be considered within the scope of the invention.

[0031] One aspect of the present invention is a polymeric compositioncapable of entrapping a large amount of a hydrophobic drug and formingstable polymeric micelles or nanoparticles in an aqueous environment.Specifically, the present invention provides a polymeric compositioncomprising an amphiphilic block copolymer composed of a hydrophilicblock and hydrophobic block, and a polylactic acid derivative having acarboxyl terminal group, wherein said composition forms stable polymericmicelles in an aqueous environment.

[0032] Another aspect of the present invention provides a polymericcomposition comprising an amphiphilic block copolymer comprised of ahydrophilic block and a hydrophobic block, and a polylactic acidderivative having a carboxyl terminal group that is bound with a di- ortri-valent metal ion.

[0033] The present invention also provides a pharmaceutical compositioncomprising polymeric micelles or nanoparticles formed by the abovepolymeric composition having a hydrophobic drug entrapped therein. Thepresent invention further provides a process for preparing the abovepharmaceutical composition.

[0034] The amphiphilic block copolymer of the present invention ispreferably an A-B type diblock copolymer comprising a hydrophilic Ablock and a hydrophobic B block. The amphiphilic block copolymer, whenplaced in an aqueous phase, forms core-shell type polymeric micelleswherein the hydrophobic B block forms the core and the hydrophilic Ablock forms the shell. Preferably, the hydrophilic A block is a memberselected from the group consisting of polyalkylene glycol, polyvinylalcohol, polyvinyl pyrrolidone, is polyacryl amide and derivativesthereof. More preferably, the hydrophilic A block is a member selectedfrom the group consisting of monomethoxypolyethylene glycol,monoacetoxypolyethylene glycol, polyethylene glycol,polyethylene-co-propylene glycol, and polyvinyl pyrrolidone. Preferably,the hydrophilic A block has a number average molecular weight of 500 to50,000 Daltons. More preferably, the hydrophilic A block has a numberaverage molecular weight of 1,000 to 20,000 Daltons.

[0035] The hydrophobic B block of the amphiphilic block copolymer of thepresent invention is a highly biocompatible and biodegradable polymerselected from the group consisting of polyesters, polyanhydrides,polyamino acids, polyorthoesters and polyphosphazine. More preferably,the hydrophobic B block is a member selected from the group consistingof polylactides, polyglycolides, polycaprolactone, polydioxan-2-one,polylactic-co-glycolide, polylactic-co-dioxan-2-one,polylactic-co-caprolactone, and polyglycolic-co-caprolactone. Thecarboxyl terminal group of the hydrophobic B block can be substitutedwith a fatty acid such as butyric acid, propionic acid, acetic acid,stearic acid or palmitic acid. Preferably, the hydrophobic B block ofthe amphiphilic block copolymer has a number average molecular weight of500 to 50,000 Daltons. More preferably, the hydrophobic B block of theamphiphilic block copolymer has a number average molecular weight 1,000to 20,000 Daltons.

[0036] The ratio of the hydrophilic A block to the hydrophobic B blockof the amphiphilic block copolymer of the present invention ispreferably within the range of 2:8 to 8:2, and more preferably withinthe range of 4:6 to 7:3. If the content of the hydrophilic A block istoo low, the polymer may not form polymeric micelles in an aqueoussolution, and if the content is too high, the polymeric micelles formedare not stable.

[0037] At least one terminal end of the polylactic acid derivative ofthe present invention is covalently bound to at least one carboxylicacid or carboxylate salt. The other terminal end of the polylactic acidderivative of the present invention may be covalently bound to afunctional group selected from the group consisting of hydroxyl,acetoxy, benzoyloxy, decanoyloxy and palmitoyloxy groups. The carboxylicacid or carboxylate salt functions as a hydrophilic group in an aqueoussolution of pH 4 or more and enables the polylactic acid derivative toform polymeric micelles therein. When the polylactic acid derivatives ofthe present invention are dissolved in an aqueous solution, thehydrophilic and hydrophobic components present in the polylactic acidderivative should be balanced in order to form polymeric micelles.Therefore, the number average molecular weight of the polylactic acidderivative of the present invention is preferably within the range of500 to 2,500 Daltons. The molecular weight of the polylactic acidderivative can be adjusted by controlling the reaction temperature,time, and the like, during the preparation process.

[0038] The polylactic acid derivative is preferably represented by thefollowing formula:

RO—CHZ-[A]_(n)-[B]_(m)-COOM   (I)

[0039] wherein A is —COO—CHZ-; B is —COO—CHY—, —COO—CH₂CH₂CH₂CH₂CH₂— or—COO—CH₂CH₂OCH₂; R is a hydrogen atom, acetyl, benzoyl, decanoyl,palmitoyl, methyl or ethyl group; Z and Y each are a hydrogen atom,methyl, or phenyl group; M is H, Na, K, or Li; n is an integer from 1 to30, and m is an integer from 0 to 20.

[0040] One end of the polylactic acid derivative of the presentinvention is covalently bound to a carboxyl group or an alkali metalsalt thereof, preferably, an alkali metal salt thereof. The metal ion inthe alkali metal salt which forms the polylactic acid derivative ismonovalent, e.g. sodium, potassium or lithium. The polylactic acidderivative in the metal ion salt form is a solid at room temperature,and is very stable because of its relatively neutral pH.

[0041] More preferably, the polylactic acid derivative is represented bythe following formula:

RO—CHZ-[COO—CHX]_(p)—[COO—CHY′]_(q)-COO—CHZ-COOM   (II)

[0042] wherein X is a methyl group; Y′ is a hydrogen atom or phenylgroup; p is an integer from 0 to 25; q is an integer from 0 to 25,provided that p+q is an integer from 5 to 25; R, Z and M are the same asdefined in Formula (I).

[0043] In addition, polylactic acid derivatives of the followingformulas (III) and (IV) are also suitable for the present invention:

RO—PLA-COO—W—M′   (III)

[0044] wherein W-M′ is

[0045] the PLA is a member selected from the group consisting ofD,L-polylactic acid, D-polylactic acid, polymandelic acid, a copolymerof D,L-lactic acid and glycolic acid, a copolymer of D,L-lactic acid andmandelic acid, a copolymer of D,L-lactic acid and caprolactone, and acopolymer of D,L-lactic acid and 1,4-dioxan-2-one; R and M are the sameas defined in Formula (I).

S—O—PLA-COO-Q   (IV)

[0046] wherein S is

[0047] L is —NR₁— or —O—; R₁ is a hydrogen atom or C₁₋₁₀alkyl; Q is CH₃,CH₂CH₃, CH₂CH₂CH₃, CH₂CH₂CH₂CH₃, or CH₂C₆H₅; a is an integer from 0 to4; b is an integer from 1 to 10; R and M are the same as defined inFormula (I); and PLA is the same as defined in Formula (III).

[0048] The polymeric composition of the present invention may contain 5to 95 wt % of the amphiphilic block copolymer and 5 to 95 wt % of thepolylactic acid derivative based on the total weight of the composition.Preferably, the polymeric composition of the present invention contains20 to 80 wt % of the amphiphilic block copolymer and 20 to 80 wt % ofthe polylactic acid derivative. More preferably, the polymericcomposition of the present invention contains 50 to 80 wt % of theamphiphilic block copolymer and 20 to 50 wt % of the polylactic acidderivative.

[0049] The polylactic acid derivatives of the present invention alonecan form micelles in an aqueous solution of pH 4 or more; however, thepolymeric compositions can form micelles in an aqueous solutionirrespective of the pH of the solution. Since the biodegradable polymeris usually hydrolyzed at a pH of 10 or more, the polymeric compositionsof the present invention may be used at a pH within the range of 1 to10, preferably at a pH within the range of 4 to 8. The particle size ofthe micelles or nanoparticles prepared from the polymeric compositionsof the present invention may be adjusted to be within the range of 1 to400 nm, and preferably from 5 to 200 nm, depending on the molecularweight of the polymers and the ratio of the polylactic acid derivativeto the amphiphilic block copolymer.

[0050] As illustrated in FIG. 1 to FIG. 3, the polylactic acidderivatives or the amphiphilic block copolymers alone and mixturesthereof may form micelles in an aqueous solution. 1 represents poorlywater-soluble drugs; 10 represents monomethoxypolyethyleneglycol-polylactide (mPEG-PLA); 11 represents monomethoxypolyethyleneglycol (mPEG); 12 represents polylactide (PLA); 20 represents the sodiumsalt of D,L-poly(lactic acid); 21 represents D,L-polylactic acid; and 22represents sodium carboxylate. However, the polymeric compositions ofthe present invention remarkably improve the drug loading efficiency andstability of the micelles formed in an aqueous solution compared withthe micelles formed from the polylactic acid derivatives or theamphiphilic block copolymers alone.

[0051] According to the following examples, the polymeric micellescomposed of the polylactic acid derivative alone may contain up to 25wt% of paclitaxel, but the paclitaxel is released within 1 hour at 37° C.in an aqueous solution. In addition, the polymeric micelles composed ofthe amphiphilic block copolymer alone may contain 5wt % or less ofpaclitaxel, and the paclitaxel is released in 6 hours at 37° C. in anaqueous solution. In contrast, the polymeric micelles composed of thecomposition of the present invention comprising an amphiphilic blockcopolymer and a polylactic acid derivative may contain up to 25 wt % ofpaclitaxel, and less than at most 1.0% (w/w)of the paclitaxel isreleased within 24 hours at 37° C. in an aqueous solution.

[0052] The loading efficiency of a drug into the polymeric micelles isin proportion to the fraction of the hydrophobic block that forms thehydrophobic core of the micelle that is formed in an aqueous solution.The stability of the polymeric micelles in an aqueous solution dependson their dynamic equilibrium in the aqueous solution, i.e. theequilibrium constant between the states of the polymeric micelle and asingle polymer dissolved in water. The polylactic acid derivative isvery hydrophobic because the hydrophilic component, namely thecarboxylic acid terminal group, comprises 10% or less of the polymer.Therefore, the polymeric micelles formed by polylactic acid derivativesalone may contain a large amount of a hydrophobic drug therein, but themicelles formed are very unstable due to electrostatic repulsion betweenthe carboxyl anionic groups present in the terminus of the polymericmicelles. On the other hand, it is difficult for micelles formed from anamphiphilic block copolymer of monomethoxypolyethylene glycol (MN: 5,000Daltons) and polylactide (MN: 4,000 Daltons) to contain a large amountof a hydrophobic drug because the hydrophobic block comprises only about40% of the polymer. However, the micelles are very stable because theterminal hydrophilic groups of the amphiphilic block copolymer arenon-ionic polyethylene glycol, which exhibit no electrostatic repulsionin contrast to the polylactic acid derivatives. Therefore, by combiningamphiphilic block copolymers and polylactic acid derivatives, thepresent invention provides a polymeric micelle composition which cansolubilize a large amount of a poorly water-soluble drug, and maintainstability for 24 hours or more.

[0053] In one embodiment of the present invention, the carboxyl terminalgroup of the polylactic acid derivative is bound or fixed with a di- ortri-valent metal ion. The metal ion-fixed polymeric composition can beprepared by adding the di- or tri-valent metal ion to the polymericcomposition of the amphiphilic block copolymer and the polylactic acidderivative. The polymeric micelles or nanoparticles may be formed bychanging the amount of the di- or tri-valent metal ion added for bindingor fixing the carboxyl terminal group of the polylactic acid derivative.

[0054] The di- or tri-valent metal ion is preferably a member selectedfrom the group consisting of Ca²⁺, Mg²⁺, Ba²⁺, Cr²⁺, Fe²⁺, Mn²⁺, Ni²⁺,Cu²⁺, Zn²⁺, and Al³⁺. The di- or tri-valent metal ion may be added tothe polymeric composition of the amphiphilic block copolymer and thepolylactic acid derivative in the form of a sulfate, chloride,carbonate, phosphate or hydroxylate, and preferably, in the form ofCaCl₂, MgCl₂, ZnCl₂, AlCl₃, FeCl₃, CaCO₃, MgCO₃, Ca₃(PO₄)₂, Mg₃(PO₄)₂,AlPO₄, MgSO₄, Ca(OH)₂, Mg(OH)₂, Al(OH)₃, or Zn(OH)₂.

[0055] As illustrated in FIGS. 4 and 5, when a monovalent metal ion atthe carboxyl terminus of the polylactic acid derivative is substitutedwith a di- or tri-valent metal ion to form a metal ionic bond, themicelles or nanoparticles formed have improved stability.

[0056] Either polymeric micelles or nanoparticles can be prepared bychanging the equivalents of the metal ion added. Specifically, if adivalent metal ion is added at 0.5 equivalents or less with respect tothe carboxyl terminal groups, the metal ion that can form bonds with thecarboxyl terminal group of the polylactic acid derivative isinsufficient, and thus, polymeric micelles are formed. If a divalentmetal ion is added at 0.5 equivalents or more, the metal ion that canform bonds with the carboxyl terminal group of the polylactic acidderivative and is sufficient to firmly fix the micelles, and thus,nanoparticles are formed.

[0057] In addition, the drug release rate from the polymeric micelles ornanoparticles may be adjusted by changing the amount of equivalents ofthe metal ion added. If the metal ion is present at 1 equivalent or lesswith respect to that of the carboxyl group of the polylactic acidderivative, the number available to bond to the carboxyl terminal groupof the polylactic acid derivative is decreased, and so the drug releaserate is increased. If the metal ion is present at 1 equivalent or more,the number available to bond to the carboxyl terminal group of thepolylactic acid derivative is increased, and so the drug release rate isdecreased. Therefore, to increase the drug release rate in the blood,fewer equivalents of the metal ion are used, and to decrease the drugrelease rate, more equivalents of the metal ion are used.

[0058] The metal ion-fixed polymeric compositions of the presentinvention may contain 5 to 95wt % of the amphiphilic block copolymer, 5to 95wt % of the polylactic acid derivative and 0.01 to 10 equivalentsof the di- or tri-valent metal ion with respect to the number ofequivalents of carboxyl terminal groups of the polylactic acidderivatives. Preferably, they contain 20 to 80wt % of the amphiphilicblock copolymer, 20 to 80wt % of the polylactic acid derivative and 0.1to 5 equivalents of the di- or tri-valent metal ion, and morepreferably, 20 to 60wt % of the amphiphilic block copolymer, 40 to 80wt% of the polylactic acid derivative and 0.2 to 2 equivalents of the di-or tri-valent metal ion.

[0059] The present invention also relates to a pharmaceuticalcomposition containing polymeric micelles or nanoparticles formed fromthe polymeric compositions of the present invention having a poorlywater-soluble drug entrapped therein. The pharmaceutical compositions ofthe present invention provide for increased plasma concentrations ofhydrophobic drugs and can be used in various pharmaceuticalformulations.

[0060] As shown in FIGS. 3 to 5, a poorly water-soluble drug is mixedwith a polymeric composition of an amphiphilic block copolymer and apolylactic acid derivative to form polymeric micelles containing thedrug therein. In order to improve its stability, a di- or tri-valentmetal ion may be added to form a metal ionic bond with the carboxylterminal group of the polylactic acid derivative and thereby formdrug-containing polymeric micelles and nanoparticles.

[0061] The term “poorly water-soluble drugs” or “hydrophobic drugs”,refers to any drug or bioactive agent which has a water solubility of 50mg/ml or less. This includes anticancer agents, antibiotics,anti-inflammatory agents, anesthetics, hormones, antihypertensiveagents, agents for the treatment of diabetes, antihyperlipidemic agents,antiviral agents, agents for the treatment of Parkinson's disease,antidementia agents, antiemetics, immunosuppressants, antiulcerativeagents, laxatives, and antimalarial agents. Examples of hydrophobicdrugs include anticancer agents such as paclitaxel, camptothecin,etoposide, doxorubicin, dausorubicin, idarubicin, ara-C, etc.,immunosuppressants such as cyclosporine A, etc. Steroidal hormones suchas testosterone, estradiol, estrogen, progesterone, triamcinolonacetate, dexamethasone, etc. and anti-inflammatory agents such astenoxicam, pyroxicam, indomethacin, COX-II inhibitors, etc., which havea very fast excretion rate from the blood, are also examples of suitablehydrophobic drugs that can be used in the present invention.

[0062] The content of the poorly water-soluble drug is preferably withinthe range of 0.1 to 30wt % based on the total weight of thepharmaceutical compositions comprising an amphiphilic block copolymer, apolylactic acid derivative, and a hydrophobic drug. The size of thedrug-containing polymeric micelles or nanoparticles may be adjusted tobe from 5 to 400 nm, preferably, from 10 to 200 nm, depending on themolecular weight of the polymers and the ratio of the amphiphilic blockcopolymer to the polylactic acid derivative.

[0063] For oral or parenteral administration of a poorly water-solubledrug, the drug is entrapped in the polymeric micelles or nanoparticlesand is thereby solubilized. Particularly, the metal ion-fixed polymericmicelles or nanoparticles are retained in the bloodstream for a longperiod of time and accumulate in the target lesions. The drug isreleased from the hydrophobic core of the micelles to exhibit apharmacological effect while the micelles are degraded.

[0064] For parenteral delivery, the drug may be administeredintravenously, intramuscularly, intraperitoneally, transnasally,intrarectally, intraocularly, or intrapulmonarily. For oral delivery,the drug is mixed with the polymeric micelles of the present invention,and then, administered in the form of a tablet, capsule, or aqueoussolution.

[0065] The metal ion-fixed polymeric micelles or nanoparticles accordingto the present invention have excellent stability, and thus, canincrease the plasma concentration of a drug. As shown in the followingExperiments and FIG. 6, Composition 1 wherein paclitaxel is entrappedwithin the metal ion-fixed polymeric micelles has a longer retentiontime of drug in the bloodstream, and so maintains an effective plasmadrug concentration for a longer period of time compared with Composition3 wherein paclitaxel is entrapped in the polymeric composition composedof the block copolymer only, and Composition 2 wherein paclitaxel isentrapped in mixed polymeric micelles of the block copolymer and thepolylactic acid.

[0066] As shown in the following Experiments and FIGS. 7 and 8,Composition 4, wherein paclitaxel is entrapped in the metal ion-fixedpolymeric composition, has a longer retention time of drug in thebloodstream, and so maintains an effective plasma drug concentration fora longer period of time as compared with the marketed paclitaxelformulation, Taxol® (Composition 5), a polysorbate ethanol formulation(Composition 6) and has a high inhibition rate on cancer growth and soexhibits high anticancer activity.

[0067] Furthermore, the present invention includes a process forpreparing the above pharmaceutical composition. Specifically, as shownin FIGS. 3 and 5, the amphiphilic block copolymer, the polylactic acidderivative, and the poorly water-soluble drug are dissolved in anorganic solvent, and then, the organic solvent is evaporated therefrom.Thereafter, the obtained mixture is added to an aqueous solution toprepare mixed polymeric micelles containing the poorly water-solubledrug. The metal ion-fixed polymeric micelles or nanoparticles areprepared by adding a di- or tri-valent metal ion to the mixed polymericmicelles thereby fixing the carboxyl terminal group of the polylacticacid derivative.

[0068] The polylactic acid derivative, the amphiphilic block copolymer,and the poorly water-soluble drug at a certain ratio can be dissolved inone or more mixed solvents selected from the group consisting ofacetone, ethanol, methanol, ethyl acetate, acetonitrile, methylenechloride, chloroform, acetic acid and dioxane. The organic solvent canbe removed therefrom to prepare a homogenous mixture of the poorlywater-soluble drug and the polymer. The homogenous mixture of the poorlywater-soluble drug and the polymeric composition of the presentinvention can be added to an aqueous solution of pH 4 to 8, at 0 to 80°C. resulting in an aqueous solution of poorly water-solubledrug-containing mixed polymeric micelles. The above drug-containingpolymeric micelle aqueous solution can then be lyophilized to preparethe polymeric micelle composition in the form of solid.

[0069] An aqueous solution containing 0.001 to 2 M of the, di- ortri-valent metal ion is added to the poorly water-solubledrug-containing mixed polymeric micelle aqueous solution. The mixture isslowly stirred at room temperature for 0.1 to 1 hour and thenlyophilized to prepare the metal ion-fixed polymeric micelle ornanoparticle composition in the form of solid.

[0070] The following examples will enable those skilled; in the art tomore clearly understand how to practice the present invention. It is tobe understood that, while the invention has been described inconjunction with the preferred specific embodiments thereof, that whichfollows is intended to illustrate and not limit the scope of theinvention. Other aspects of the invention will be apparent to thoseskilled in the art to which the invention pertains.

EXAMPLES Preparations 1-11: Synthesis of polylactic acid Derivatives

[0071] The polymer was prepared by the polymerization of a2-hydroxycarboxylic acid derivative in the absence of a catalyst, at anelevated temperature (100 to 200° C.) and under reduced pressure (100 to0.1 mmHg) for 6 to 24 hours, followed by purification.

Preparation 1: Synthesis 1 of D,L-polylactic acid (PLA-COOH)

[0072] One hundred grams of D,L-lactic acid were introduced into a 250ml three-neck round-bottomed flask. The flask was equipped with astirrer, and heated in an oil bath to 80° C. The reaction was performedfor 1 hour with the pressure reduced to 25 mmHg by a vacuum a spiratorto remove excessive moisture. The reaction was then performed at atemperature of 150° C. under a reduced pressure of 25 mmHg for 6 hours.The resulting product was added to 1 liter of distilled water toprecipitate the polymer. The precipitated polymer was then added todistilled water to remove the low molecular weight polymer that wassoluble in an aqueous solution of pH 4 or less. The precipitated polymerwas then added to 1 liter of distilled water, and the pH of the aqueoussolution was adjusted to 6 to 8 by addition of sodium hydrogen carbonateportionwise thereto to dissolve the polymer. The water-insoluble polymerwas separated and removed by centrifugation or filtration. A 1 Nhydrochloric acid solution was added dropwise thereto and the polymerwas precipitated in the aqueous solution. The precipitated polymer waswashed twice with distilled water, isolated and dried under reducedpressure to obtain a highly viscous liquid (78 g of D,L-polylactic acid,yield: 78%). The number average molecular weight of the polymer was 540Daltons as determined by ¹H-NMR spectrum assay.

Preparations 2-4: Synthesis 2 of D,L-polylactic acid (PLA-COOH)

[0073] D,L-polylactic acid was obtained according to the same procedureas in Preparation 1 except for control of the reaction temperature,pressure, and time as set forth in Table 1. The number average molecularweight and the yield of D,L-polylactic acid synthesized from the abovePreparations 1 to 4 are shown in the following Table 1. TABLE 1 Prepa-Temperature Time Pressure Yield ration (° C.) (hours) (mmHg) Mn (%) 1150 6 25 540 78 2 160 12 10 1140 83 3 160 24 10 1550 84 4 160 24 5 210087

Preparation 5: Synthesis 1 of the Copolymer of D,L-lactic acid andglycolic acid (PLGA-COOH)

[0074] Fifty-five grams of D,L-lactic acid(0.6 moles) and 45 gramsglycolic acid(0.6 moles) were introduced together into a 250 mlthree-neck round-bottomed flask. The same procedure as in Preparation 1was carried out except that the reaction was performed at a temperatureof 150° C. and under a reduced pressure of 10 mmHg for 12 hours.

Preparation 6: Synthesis 2 of the Copolymer of D,L-lactic acid andglycolic acid (PLGA-COOH)

[0075] Seventy-three grams D,L-lactic acid(0.8 moles) and 27 gramsglycolic acid(0.35 moles) were introduced together into a 250 mlthree-neck round-bottomed flask. The same procedure as in Preparation 1was carried out except that the reaction was performed at a temperatureof 160° C. and under a reduced pressure of 10 mmHg for 12 hours.

Preparation 7: Synthesis 3 of the Copolymer of D,L-lactic acid andglycolic acid (PLGA-COOH)

[0076] Ninety-one grams D,L-lactic acid(1.0 mole) and 9 grams glycolicacid(0.12 moles) were introduced together into a 250 ml three-neckround-bottomed flask. The same procedure as in Preparation 1 was carriedout except that the reaction was performed at a temperature of 160° C.and under a reduced pressure of 10 mmHg for 12 hours.

Preparation 8: Synthesis 4 of the Copolymer of D,L-lactic acid andglycolic acid (PLGA-COOH)

[0077] Seventy-three grams D,L-lactic acid(0.8 moles) and 27 gramsglycolic acid(0.35 moles) were introduced into a 250 ml three-neckround-bottomed flask. The same procedure as in Preparation 1 was carriedout except that the reaction was performed at a temperature of 180° C.and under a reduced pressure of 5 mmHg for 24 hours.

[0078] The copolymers synthesized in the above Preparations 5 to 8 areshown in Table 2. TABLE 2 Molar ratio of lactic acid and glycolicReaction acid temperature Reaction Pressure Mn Yield PreparationReactant Product (° C.) time (hrs) (mmHg) (Daltons) (%) 5 50/50 52/48150 12 10 920 63 6 70/30 67/33 160 12 10 1040 65 7 90/10 91/9  160 12 101180 68 8 70/30 71/29 180 24 5 1650 73

Preparation 9: Synthesis of the Copolymer of D,L-lactic acid andmandelic acid (PLMA-COOH)

[0079] Seventy-five grams D,L-lactic acid(0.83 moles) and 25 gramsD,L-mandelic acid(0.16 moles) were introduced together into a 250 mlthree-neck round-bottomed flask. The same procedure as in Preparation 1was carried out except that the reaction was performed a temperature of180° C. and under a reduced pressure of 10 to 20 mmHg for 5 hours.Fifty-four grams (yield: 54%) of a copolymer of D,L-lactic acid andmandelic acid were obtained. The molar ratio of D,L-lactic acid tomanidelic acid was 85/15. The number average molecular weight of thepolymer was 1,096 Daltons as determined by ¹H-NMR spectrum assay.

Preparation 10: Synthesis of acetoxy D,L-polylactic acid Derivative(AcO-PLA-COOH)

[0080] Fifty grams of D,L-polylactic acid (Mn: 1,140 Daltons),synthesized from Preparation 2, and 20 ml of chloracetic acid wereintroduced together into a 250 ml round-bottomed flask. The flask wasequipped with a refrigerator, and the reaction mixture was refluxedunder nitrogen flow for 4 hours. Excessive chloracetic acid was removedby distillation, and then, the reaction product was added to a mixtureof ice and water. The whole mixture was stirred slowly to precipitatethe polymer. The precipitated polymer was separated, washed twice withdistilled water, and then, dissolved in anhydrous acetone. Anhydrousmagnesium sulfate was added thereto to remove excessive moisture. Theproduct obtained was filtered to remove the magnesium sulfate. Acetonewas removed using a vacuum evaporator thereby obtaining liquid acetoxyD,L-polylactic acid (46 g, yield: 92%). By ¹H-NMR, the acetoxy group wasidentified as a single peak at 2.02 ppm.

Preparation 11: Synthesis of palmitoyloxy D,L-polylactic acid Derivative(PalmO-PLA-COOH)

[0081] Twenty grams D,L-polylactic acid (Mn:1,140 Daltons), synthesizedfrom Preparation 2, was introduced into a 250 ml round-bottomed flask.The reactant was completely dehydrated under vacuum in an oil bath of120° C. The oil bath was cooled to 50° C. and 50 ml acetone was addedthereto to completely dissolve the polymer. 5 ml of chloropalmitic acidwas added, and the reaction was performed at a temperature of 50° C. for10 hours under nitrogen. The reaction product was washed with anexcessive amount of hexane to remove any residual reactant. The productwas then dissolved in acetone and the solution was added to a mixture ofice and water. The whole mixture was stirred slowly resulting in theprecipitation of an oligomer. The oligomer was separated and washedtwice with distilled water, and then dissolved in anhydrous acetone.Anhydrous magnesium sulfate was added to the solution to removeexcessive moisture. The product obtained was filtered to remove themagnesium sulfate. Acetone was removed with a vacuum evaporator therebyobtaining a palmitoyloxy D,L-polylactic acid derivative (19.1 g, yield:96%). By ¹H-NMR, the palmitoyl group was identified as peaks of 0.88,1.3 and 2.38 ppm.

Preparations 12 to 22: Synthesis of Carboxylate Salts of polylactic acidDerivatives

[0082] The polylactic acid derivatives synthesized from Preparations 1to 11 were reacted with basic aqueous solutions of sodium hydrogencarbonate, sodium carbonate, potassium hydrogen carbonate, or potassiumcarbonate, in an acetone solvent, to prepare their carboxylate salts.

Preparation 12: Synthesis 1 of Sodium Salt of polylactic acid(PLA-COONa)

[0083] D,L-polylactic acid (Mn: 540 Daltons) synthesized fromPreparation 1 was dissolved in acetone. The solution was introduced intoa round-bottomed flask and the flask was equipped with a stirrer. Thesolution was stirred slowly at room temperature and a sodium hydrogencarbonate solution (1 N) was slowly added thereto until a pH of 7 wasreached. Anhydrous magnesium sulfate was added thereto and excessivemoisture was removed therefrom. The mixture obtained was filtered andthe acetone was evaporated with a solvent evaporator. A white solid wasobtained. The solid was dissolved in anhydrous acetone and the solutionwas filtered to remove the insoluble portion. Acetone was evaporatedleaving the sodium salt of D,L-polylactic acid (yield: 96%) as a whitesolid. As shown in FIG. 2, a hydrogen peak adjacent to the carboxylicacid group was observed at 4.88 ppm by ¹H-NMR, and the polymer whendissolved in water had a pH of 6.5 to 7.5.

Preparation 13: Synthesis 2 of the Sodium Salt of polylactic acid(PLA-COONa)

[0084] The sodium salt of polylactic acid (yield: 95%) was synthesizedaccording to the same procedure as in the above Preparation 12 exceptthat D,L-polylactic acid (Mn: 1,140 Daltons) synthesized fromPreparation 2 and an aqueous solution of sodium carbonate were used.

Preparation 14: Synthesis of the Sodium Salt of acetoxy-D,L-polylacticacid (AcO-PLA-COONa)

[0085] The sodium salt of acetoxy-D,L-polylactic acid (yield: 95%) wassynthesized according to the same procedure as in Preparation 12 exceptthat acetoxy-D,L-polylactic acid (Mn: 1,140 Daltons) synthesized fromPreparation 10 and an aqueous solution of sodium carbonate were used.

Preparation 15: Synthesis 1 of Sodium Salt of palmitoyloxyD,L-polylactic acid (PalmO-PLA-COONa)

[0086] The palmitoyloxy D,L-polylactic acid (Mn: 1,140 Daltons)synthesized from Preparation 11 was completely dissolved in an aqueoussolution o f acetone (28.6v/v %). The solution was introduced into around-bottomed flask and the flask was equipped with a stirrer. Thesolution was stirred slowly at room temperature, and then, an aqueoussolution of sodium hydrogen carbonate (1 N) was added thereto forneutralization. The solution was stirred slowly at room temperature andsodium hydrogen carbonate solution (1 N) was slowly added thereto untila pH of 7 was reached. Anhydrous magnesium sulfate was added thereto toremove excessive moisture. The solution obtained was filtered and theacetone was evaporated with a solvent evaporator. A white solid wasobtained. The solid was dissolved in acetone and the solution wasfiltered to remove any particles that were insoluble in acetone. Theacetone was evaporated and the sodium salt of palmitoyloxyD,L-polylactic acid was obtained as a white solid (yield: 96%).

Preparation 16: Synthesis 2 of the Potassium Salt of polylactic acid(PLA-COOK)

[0087] The potassium salt of polylactic acid (yield: 98%) wassynthesized according to the same procedure as in Preparation 12 exceptthat D,L-lactic acid (Mn: 1,550 Daltons) synthesized from Preparation 3and an aqueous solution of potassium hydrogen carbonate were used.

Preparation 17: Synthesis 3 of the Sodium Salt of polylactic acid(PLA-COONa)

[0088] The sodium salt of polylactic acid (yield: 95%) was synthesizedaccording to the same procedure as in Preparation 12 except thatD,L-lactic acid (Mn: 2,100 Daltons) synthesized from Preparation 4 wasused.

Preparation 18: Synthesis 1 of the Sodium Salt of a Copolymer ofD,L-lactic acid and glycolic acid (PLGA-COONa)

[0089] The sodium salt of a copolymer of D,L-lactic acid and glycolicacid (yield: 98%) was synthesized according to the same procedure as inPreparation 12 except that a copolymer of D,L-lactic acid and glycolicacid (Mn: 920 Daltons) synthesized from Preparation 5 and an aqueoussolution of sodium carbonate were used.

Preparation 19: Synthesis 2 of the Sodium Salt of a Copolymer ofD,L-lactic acid and glycolic acid (PLGA-COONa)

[0090] The sodium salt of a copolymer of D,L-lactic acid and glycolicacid (yield: 93%) was synthesized according to the same procedure as inPreparation 12 except that a copolymer of D,L-lactic acid and glycolicacid (Mn: 1,040 Daltons) synthesized from Preparation 6 was used.

Preparation 20: Synthesis of the Potassium Salt of a Copolymer ofD,L-lactic acid and glycolic acid (PLGA-COOK)

[0091] The potassium salt of a copolymer of D,L-lactic acid and glycolicacid (yield: 92%) was synthesized according to the same procedure as inPreparation 12 except that a copolymer of D,L-lactic acid and glycolicacid (Mn: 1,180 Daltons) synthesized from Preparation 7 and an aqueoussolution of potassium carbonate were used.

Preparation 21: Synthesis 3 of the Sodium Salt of a Copolymer ofD,L-lactic acid and glycolic acid (PLGA-COONa)

[0092] The sodium salt of a copolymer of D,L-lactic acid and glycolicacid (yield: 98%) was synthesized according to the same procedure as inPreparation 12 except that a copolymer of D,L-lactic acid and glycolicacid (Mn: 1,650 Daltons) synthesized from Preparation 8 was used.

Preparation 22: Synthesis of the Sodium Salt of a Copolymer ofD,L-lactic acid and mandelic acid (PLMA-COONa)

[0093] The sodium salt of a copolymer of D,L-lactic acid and mandelicacid (yield: 96%) was synthesized as white solid according to the sameprocedure as in Preparation 12 except that a copolymer of D,L-lacticacid and mandelic acid synthesized from Preparation 9 (Mn: 1,096Daltons) was used.

[0094] The carboxylate salts of the polylactic acid derivativessynthesized from the above Preparations 12 to 22 are shown in Table 3.TABLE 3 Prepa- Reactant Mn Yield ration (MN) Base Product (Daltons) (%)12 PLA-COOH NaHCO₃ PLA-COONa 540 96 (540) 13 PLA-COOH Na₂CO₃ PLA-COONa1,140 95 (1,140) 14 AcO-PLA-COOH Na₂CO₃ AcO-PLA-COONa 1,140 95 (1,140)15 Palmitoyl NaHCO₃ Palmitoyl 1,140 96 O-PLA-COOH O-PLA-COONa (1,140) 16PLA-COOH KHCO₃ PLA-COOK 1,550 98 (1,550) 17 PLA-COOH NaHCO₃ PLA-COONa2,100 95 (2,100) 18 PLGA-COOH Na₂CO₃ PLGA-COONa 920 98 (920) 19PLGA-COOH NaHCO₃ PLGA-COONa 1,040 93 (1,040) 20 PLGA-COOH K₂CO₃PLGA-COOK 1,180 92 (1,180) 21 PLGA-COOH NaHCO₃ PLGA-COONa 1,650 98(1,650) 22 PLMA-COOH NaHCO₃ PLMA-COONa 1,096 96 (1,096)

Preparations 23 to 29: Synthesis of an AB Type Block Copolymer Composedof a Hydrophilic A Block and a Hydrophobic B Block Preparation 23:Polymerization of a monomethoxypolyethylene glycol-polylactide(mPEG-PLA) Block Copolymer (AB Type)

[0095] Five grams of monomethoxypolyethylene glycol (Mn: 2,000 Daltons)was introduced into a 100 ml two-neck round-bottomed flask, anddehydrated by heating to 130° C. under a reduced pressure (1 mmHg) for 3to 4 hours. The reaction flask was filled with dried nitrogen and areaction catalyst, stannous octoate (Sn(Oct)₂), was injected with 0.1 wt% (10.13 mg, 25 mmol) of D,L-lactide using a syringe. The reactionmixture was stirred for 30 minutes, the pressure was reduced to 1 mmHgat 130° C. for 1 hour to remove the solvent (toluene) dissolving thecatalyst. Purified lactide (10.13 g) was added thereto, and the mixturewas heated to 130° C. for 18 hours. The polymer formed was dissolved inmethylene chloride, and diethyl ether was added thereto to precipitatethe polymer. The polymer obtained was dried in a vacuum oven for 48hours. The mPEG-PLA obtained had the number average molecular weight of2,000-1,765 Daltons, and was confirmed to be of the AB type by ¹H-NMR.

Preparation 24: Polymerization of a monomethoxypolyethyleneglycol-polylactide (mPEG-PLA) Block Copolymer (AB type)

[0096] Five grams of monomethoxypolyethylene glycol (Mn: 2,000 Daltons)was introduced into a 100 ml two-neck round-bottomed flask, anddehydrated by heating to 130° C. under a reduced pressure (1 mmHg) for 3to 4 hours. The reaction flask was filled with dried nitrogen and areaction catalyst, stannous octoate (Sn(Oct)₂), was injected with 0.1 wt% (13.75 mg, 34 mmol) of D,L-lactide using a syringe. The reactionmixture was stirred for 30 minutes, the pressure was reduced to 1 mmHgat 130° C. for 1 hour to remove the solvent (toluene) dissolving thecatalyst. Purified lactide (13.75 g) was added thereto, and the mixturewas heated to 130° C. for 18 hours. The polymer formed was dissolved inmethylene chloride, and diethyl ether was added thereto to precipitatethe polymer. The polymer obtained was dried in a vacuum oven for 48hours. The mPEG-PLA obtained had a number average molecular weight of2,000-5,000 Daltons, and was confirmed to be of the AB type by ¹H-NMR.

Preparation 25: Polymerization of a monomethoxypolyethyleneglycol-polylactide (mPEG-PLA) Block Copolymer (AB Type)

[0097] Five grams of monomethoxypolyethylene glycol (Mn: 2,000 Daltons)was introduced into a 100 ml two-neck round-bottomed flask, anddehydrated by heating to 130° C. under a reduced pressure (1 mmHg) for 3to 4 hours. The reaction flask was filled with dried nitrogen and areaction catalyst, stannous octoate (Sn(Oct)₂), was injected with 0.1 wt% (22.0 mg, 55 mmol) of D,L-lactide using a syringe. The reactionmixture was stirred for 30 minutes, the pressure was reduced to 1 mmHgat 130° C. for 1 hour to remove the solvent (toluene) dissolving thecatalyst. Purified lactide (22 g) was added thereto, and the mixture washeated to 130° C. for 18 hours. The polymer formed was dissolved inmethylene chloride, and diethyl ether was added thereto to precipitatethe polymer. The polymer obtained was dried in a vacuum oven for 48hours. The mPEG-PLA obtained had a number average molecular weight of2,000-8,000 Daltons, and was confirmed to be of the AB type by ¹H-NMR.

Preparation 26: Polymerization of a monomethoxypolyethyleneglycol-poly(lactic-co-glycolide) (mPEG-PLGA) Block Copolymer (AB Type)

[0098] To synthesize the mPEG-PLGA block copolymer,monomethoxypolyethylene glycol (Mn: 5,000 Daltons) was reacted withlactide and glycolide in the presence of the catalyst, stannous octoate,at 120° C. for 12 hours according to the same procedure as inPreparation 23. The mPEG-PLGA obtained had a number average molecularweight of 5,000-4,000 Daltons, and was confirmed to be of the AB type by¹H-NMR.

Preparation 27: Polymerization of a monomethoxypolyethyleneglycol-poly(lactic-co-p-dioxan-2-one) (mPEG-PLDO) Block Copolymer (ABType)

[0099] To synthesize a MPEG-PLDO block copolymer,monomethoxypolyethylene glycol (Mn: 12,000 Daltons) was reacted withlactide and p-dioxan-2-one in the presence of the catalyst, stannousoctoate, at 110° C. for 12 hours according to the same procedure as inPreparation 23. The mPEG-PLDO obtained had a number average molecularweight of 12,000-10,000 Daltons, and was confirmed to be of the AB typeby ¹H-NMR.

Preparation 28: Polymerization of a monomethoxypolyethyleneglycol-polycaprolactone (mPEG-PCL) Block Copolymer (AB Type)

[0100] To synthesize a mPEG-PCL block copolymer, monomethoxypolyethyleneglycol (Mn: 12,000 Daltons) was reacted with caprolactone in thepresence of the catalyst, stannous octoate, at 130° C. for 12 hours,according to the same procedure as in Preparation 23. The mPEG-PCLobtained had a number average molecular weight of 12,000-5,000 Daltons,and was confirmed be of the AB type by ¹H-NMR.

Preparation 29: Polymerization of a monomethoxypolyethyleneglycol-polylactide-palmitate (mPEG-PLA-palmitate) Block Copolymer (ABType)

[0101] The synthesized monomethoxypolyethylene glycol-polylactide(mPEG-PLA) (Mn: 2,000-1,750, 20 g) was introduced into a flask andcompletely dehydrated under vacuum in an oil bath at 120° C. Thereactant was cooled to 50° C. and 50 ml of acetone was added thereto inorder to completely dissolve the polymer. 2 ml of palmitoyl chloride wasadded thereto (molar ratio: palmitoyl chloride/mPEG-PLA=1.2/1), and thereaction was performed at 50° C. under nitrogen flow for 10 hours. Thereaction mixture was washed with excess hexane to remove any residualreactant. The polymer obtained was dissolved in methylene chloride,precipitated with diethyl ether and then filtered. The polymer obtainedwas dried in a vacuum oven for 48 hours. The mPEG-PLA-palmitate obtainedhad a Mn of 2,000-1,800 Daltons. In addition, it was confirmed by ¹H-NMRthat a palmitoyl group was bonded to the —OH terminal group of theMPEG-PLA.

[0102] The block copolymers synthesized from the above Preparations 23to 29 are the following Table 4. TABLE 4 Preparation Amphiphilic blockcopolymer Mn (Daltons) Yield (%) 23 mPEG-PLA 2,000-1,765 86 24 mPEG-PLA2,000-5,000 87 25 mPEG-PLA 2,000-8,000 85 26 mPEG-PLGA 5,000-4,000 90 27mPEG-PLDO 12,000-10,000 78 28 mPEG-PCL 12,000-5,000  93 29mPEG-PLA-palmitate 2,000-1,800 90

Examples 1 to 7 Preparation of Poorly Water-Soluble Drug-ContainingMixed Polymeric Micelles Example 1 Preparation of aPaclitaxel-Containing Mixed Polymeric Micelle Composition ofD,L-PLA-COONa and mPEG-PLGA Block Copolymers

[0103] D,L-PLA-COONa (Mn: 1,140 Daltons)(130 mg), synthesized from theabove Preparation, an amphiphilic block copolymer mPEG-PLGA (Mn:5,000-4,000 Daltons)(100 mg), and 40 mg paclitaxel were dissolved in 1ml of acetone to prepare a clear solution. Acetone was removed therefromto prepare the paclitaxel-containing mixed polymeric composition.Distilled water(2 ml) was added to the paclitaxel-containing polymericcomposition, and the mixture was stirred for 20 minutes at 40° C. toprepare the paclitaxel-containing mixed polymeric micelle aqueoussolution. The solution was passed through a filter having a pore size of200 nm to remove any undissolved paclitaxel. The content and solubilityof paclitaxel were determined by HPLC and the particle size was measuredby a Dynamic Light Scattering (DLS) Method.

[0104] D,L-PLA-COONa/mPEG-PLGA=56/44

[0105] Content of paclitaxel: 14.8 wt %

[0106] Solubility of paclitaxel in an aqueous solution: 40 mg/ml

[0107] Particle size: 24 nm

Example 2 Preparation of a Paclitaxel-Containing Mixed Polymeric MicelleComposition of D,L-PLA-COONa and mPEG-PLA Block Copolymer

[0108] D,L-PLA-COONa (Mn: 1,140 Daltons)(180 mg), synthesized from theabove Preparation, 100 mg of the amphiphilic block copolymer mPEG-PLA(Mn: 2,000-1,765 Daltons), and 20 mg of paclitaxel were dissolved in 1ml of acetone to prepare a clear solution. Acetone was removed therefromto prepare a paclitaxel-containing mixed polymeric composition.Distilled water(2 ml) was added to the paclitaxel-containing polymericcomposition, and the mixture was stirred for 30 minutes at 40° C. toprepare the paclitaxel-containing mixed polymeric micelle aqueoussolution. The solution was passed through a filter having a pore size of200 nm to remove any undissolved paclitaxel.

[0109] D,L-PLA-COONa/mPEG-PLA=64/36

[0110] Content of paclitaxel: 6.7 wt %

[0111] Solubility of paclitaxel in an aqueous solution: 10 mg/ml

[0112] Particle size: 16 nm

Example 3 Preparation of a Cyclosporine A-Containing Mixed PolymericMicelle Composition of D,L-PLGA-COONa and mPEG-PLA Block Copolymers

[0113] A cyclosporine A-containing mixed polymeric micelle aqueoussolution was prepared according to the same procedure as in Example 2except that 150 mg of D,L-PLGA-COONa (Mn: 1,650 Daltons) synthesizedfrom the above Preparation, 50 mg of the amphiphilic block copolymerMPEG-PLA (Mn: 2,000-,1765 Daltons), and 20 mg of cyclosporine A wereused, and passed through a filter having a pore size of 200 nm to removeany undissolved cyclosporine A.

[0114] D,L-PLGA-COONa/mPEG-PLA=75/25

[0115] Content of cyclosporine A: 9.1 wt %

[0116] Particle size: 20 nm

Example 4 Preparation of a Cyclosporine A-Containing Mixed PolymericMicelle Composition of D,L-PLA-COONa and mPEG-PLA Block Copolymers

[0117] A cyclosporine A-containing mixed polymeric micelle aqueoussolution was prepared according to the same procedure as in Example 2except that 100 mg of D,L-PLA-COONa (Mn: 540 Daltons) synthesized fromthe above Preparation, 100 mg of the amphiphilic block copolymerMPEG-PLA (Mn: 2,000-1,765 Daltons), and 25 mg of cyclosporine A wereused.

[0118] D,L-PLA-COONa/mPEG-PLA=50/50

[0119] Content of cyclosporine A: 11.1 wt %

[0120] Particle size: 22 nm

Example 5 Preparation of a Cyclosporine A-Containing Mixed PolymericMicelle Composition of D,L-PLGA-COONa and mPEG-PLA Block Copolymers

[0121] A cyclosporine A-containing mixed polymeric micelle aqueoussolution was prepared according to the same procedure as in Example 2except that 100 mg of D,L-PLGA-COONa (Mn: 1,040 Daltons) synthesizedfrom the above Preparation, 100 mg of the amphiphilic block copolymermPEG-PLA (Mn: 2,000-,1765 Daltons), and 25 mg of cyclosporine A wereused.

[0122] D,L-PLGA-COONa/mPEG-PLA=50/50

[0123] Content of cyclosporine A: 11.1 wt %

[0124] Particle size: 24 nm

Example 6 Preparation of a Paclitaxel-Containing Mixed Polymeric MicelleComposition of D,L-PLA-COONa and mPEG-PLA Block Copolymer

[0125] A paclitaxel-containing mixed polymeric micelle aqueous solutionwas prepared according to the same procedure as in Example 2 except thatD,L-PLA-COONa (Mn: 1,140 Daltons)(100 mg), synthesized from the abovePreparation, 90 mg of the amphiphilic block copolymer mPEG-PLA (Mn:2,000-5,000 Daltons), and 10 mg of paclitaxel were used.

[0126] D,L-PLA-COONa/mPEG-PLA=54/46

[0127] Content of paclitaxel: 5.0 wt %

[0128] Solubility of paclitaxel in an aqueous solution: 10 mg/ml

[0129] Particle size: 56 nm

Example 7 Preparation of a Paclitaxel-Containing Mixed Polymeric MicelleComposition of D,L-PLA-COONa and mPEG-PLA Block Copolymer

[0130] A paclitaxel-containing mixed polymeric micelle aqueous solutionwas prepared according to the same procedure as in Example 2 except thatD,L-PLA-COONa (Mn: 1,140 Daltons)(150 mg), synthesized from the abovePreparation, 90 mg of the amphiphilic block copolymer mPEG-PLA (Mn:2,000-8,000 Daltons), and 10 mg of paclitaxel were used.

[0131] D,L-PLA-COONa/mPEG-PLA=63/37

[0132] Content of paclitaxel: 4.0 wt %

[0133] Solubility of paclitaxel in an aqueous solution: 10 mg/ml

[0134] Particle size: 56 nm

Comparative Example 1 Preparation of Paclitaxel-Containing PolymericMicelles of D,L-PLA-COONa

[0135] D,L-PLA-COONa (Mn: 1,140 Daltons)(80 mg) synthesized from theabove Preparation and 20 mg of paclitaxel were dissolved in 1 ml ofacetone. The acetone was removed using a vacuum evaporator and distilledwater was added thereto to prepare paclitaxel-containing D,L-PLA-COONapolymeric micelles. The mixture obtained was passed through a filterhaving a pore size of 200 nm to remove any undissolved paclitaxel. Thecontent and solubility of paclitaxel, and particle size were as follows:

[0136] Content of paclitaxel: 20 wt %

[0137] Solubility of paclitaxel in an aqueous solution: 20 mg/ml

[0138] Particle size: 18 nm

Comparative Example 2 Preparation of Paclitaxel-Containing mPEG-PLGAPolymeric Micelles

[0139] mPEG-PLGA (Mn: 5,000-4,000 Daltons)(80 mg) synthesized from theabove Preparation and 20 mg of paclitaxel were dissolved in 1 ml ofacetone. The acetone was removed using a vacuum evaporator and distilledwater was added thereto to prepare paclitaxel-containing mPEG-PLGApolymeric micelles.

[0140] Content of paclitaxel: 5 wt %

[0141] Solubility of paclitaxel in an aqueous solution: 5 mg/ml

[0142] Particle size: 28 nm

Experimental Example 1 Stability Test

[0143] The drug loading efficiency and stability at 37° C. of an aqueoussolution of the paclitaxel-containing mixed polymeric micellecomposition obtained from Example 1 was compared with that of theD,L-PLA-COONa polymeric micelle composition obtained from ComparativeExample 1 and the mPEG-PLGA polymeric micelle composition obtained fromComparative Example 2. The drug loading efficiency of the polymericmicelles was calculated by preparing polymeric micelles containingexcessive drug, passing them through a filter having a pore size of 200nm, measuring the drug concentration in the filtrate by HPLC, andreducing the measured concentration to weight % of the drug on the basisof the total weight of the polymeric micelle composition. The resultsare shown in Table 5. TABLE 5 Comparative Comparative Example 1 Example1 Example 2 Loading efficiency (%) 14.8 20 5

[0144] FIGS. 1 to 3 are schematic diagrams of the polymeric micelles ofthe above Example 1 and Comparative Examples 1 and 2.

[0145] As shown in Table 5, the loading efficiency of paclitaxel was14.8 wt % in the mixed polymeric micelles and 20 wt % in theD,L-PLA-COONa polymeric micelles, whereas it was only 5 wt % in themPEG-PLGA polymeric micelles. Consequently, it was demonstrated that themPEG-PLGA polymeric micelles had only about ⅓ of the loading efficiencyas compared with other polymeric micelles, and the mixed polymericmicelles of the present invention had a loading efficiency similar tothe D,L-PLA-COONa.

[0146] The polymeric micelles were diluted in a phosphate bufferedsaline solution with a pH of 7 to adjust the concentration of paclitaxelto 1 mg/ml. Then, the concentration of paclitaxel was measured at timeintervals while incubating at 37° C. The results are shown in Table 6.TABLE 6 Stability of mixed and single polymeric micelles at 37° C.Concentration of paclitaxel (mg/ml) Comparative Comparative HoursExample 1 Example 1 Example 2 0 1.0 1.0 1.0 1 1.0 0.6 1.0 6 1.0 0.4 0.912 1.0 0.3 0.5 24 1.0 0.3 0.4

[0147] As shown in Table 6, paclitaxel was not released within 24 hoursfrom the mixed polymeric micelle composition of Example 1. In contrast,paclitaxel was released in a burst after 1 hour from the D,L-PLA-COONapolymeric micelle composition of Comparative Example 1 and after 6 hoursfrom the mPEG-PLGA polymeric micelle composition of Comparative Example2. Only about 40% of the drug remained after 24 hours in the mPEG-PLGApolymeric micelle composition of Comparative Example 2. The aboveresults demonstrate that the mixed polymeric micelle composition of thepresent invention has stability comparable to the mPEG-PLGA polymericmicelle composition of Comparative Example 2.

Experimental Example 2 Evaluation of the Effect of the Composition Ratioof the Polymers to the Stability of Poorly Water-Soluble Drug-ContainingMixed Polymeric Micelles

[0148] Compositions containing 9.1 wt % of paclitaxel, on the basis ofthe total weight of the composition, were prepared according to theprocedure in Example 1. The composition ratios of D,L-PLA-COONa (Mn:1,140 Daltons) to mPEG-PLA (Mn: 2,000-1,765 Daltons) were changed asfollows: 0/100, 10/90, 20/80, 40/60, 50/50, 60/40, 80/20, 90/10, and100/0. The compositions were then diluted in a phosphate bufferedsolution at a pH of 7 to adjust the concentration of paclitaxel to 1mg/ml. The concentration of paclitaxel was measured at time intervalswhile incubating at 25° C. to compare the micelle stability. The resultsare shown in Table 7. TABLE 7 Comparison of the stability at 25° C.depending on the composition ratio of the polylactic acid derivative andthe amphiphilic block copolymer D,L-PLA- mPEG- Initial Conc. after Conc.after COONa PLA Paclitaxel Conc. 12 hrs 24 hrs (mg) (mg) (mg) (mg/ml)(mg/ml) (mg/ml) — 100 10 1.0 0.65 0.2 10 90 10 1.0 1.0 0.83 20 80 10 1.01.0 1.0 40 60 10 1.0 1.0 1.0 50 50 10 1.0 1.0 1.0 60 40 10 1.0 1.0 1.080 20 10 1.0 1.0 1.0 90 10 10 1.0 1.0 0.94 100 — 10 1.0 0.37 0.32

[0149] As shown in Table 7, the mixed polymeric micelles of the presentinvention had a constant paclitaxel concentration even after 24 hours,while the single polymeric micelles comprising a polylactic acidderivative or an amphiphilic block copolymer had a decreased paclitaxelconcentration after 12 hours. Consequently, it was demonstrated that themixed polymeric micelles had better stability than the single polymericmicelles.

Examples 8 to 13 Preparation of Di- or Tri-Valent Metal Ion-Fixed PoorlyWater-Soluble Drug-Containing Micelles or Nanoparticles Example 8Preparation of Ca²⁺-Fixed Paclitaxel-Containing Micelles ofD,L-PLA-COONa and MPEG-PLA Block Copolymers Step 1: Preparation ofPaclitaxel-Containing Polymeric Micelles of D,L-PLA-COONa and mPEG-PLABlock Copolymers

[0150] For this step, 130 mg (114 mmol) of D,L-PLA-COONa (Mn: 1,140) ofPreparation 13, 30 mg of paclitaxel, and 100 mg of mPEG-PLA (Mn:2,000-1,765 Daltons) of Preparation 23 were completely dissolved in 2 mlof acetone to obtain a clear solution. Acetone was removed therefrom toprepare a paclitaxel-containing polymeric composition. Distilledwater(2.5 ml) was added thereto and the mixture was stirred for 30minutes at 40° C. to prepare the paclitaxel-containing polymeric micelleaqueous solution.

Step 2: Fixation with the Divalent Metal Ion

[0151] For this step, 0.29 ml (58 mmol) of a 0.2 M aqueous solution ofanhydrous calcium chloride was added to the polymeric micelle aqueoussolution prepared in Step 1, and the mixture was stirred for 20 minutesat room temperature. The mixture was passed through a filter having apore size of 200 nm, and then was lyophilized. The content andsolubility of paclitaxel were measured by HPLC and the particle size wasmeasured according to a Dynamic Light Scattering (DLS) Method.

[0152] D,L-PLA-COONa/mPEG-PLA (weight ratio): 56.5/43.5

[0153] Content of paclitaxel: 11.5 wt %

[0154] Solubility of paclitaxel in the aqueous solution: 10.7 mg/ml

[0155] Particle size: 18 nm

Example 9 Preparation of Mg²⁺-Fixed Paclitaxel-Containing PolymericMicelles of D,L-PLA-COONa and mPEG-PLA Block Copolymers

[0156] In this example, 0.29 ml (58 mmol) of a 0.2 M anhydrous magnesiumchloride aqueous solution was added to the polymeric micelle aqueoussolution prepared in Step 1 of the above Example 8 and the mixture wasstirred for 20 minutes at room temperature. The mixture was passedthrough a filter having a pore size of 200 nm, and then was lyophilized.

[0157] D,L-PLA-COONa/mPEG-PLA (weight ratio): 56.5/43.5

[0158] Content of paclitaxel: 11.5 wt %

[0159] Solubility of paclitaxel in the aqueous solution: 10.7 mg/ml

[0160] Particle size: 18 nm

Example 10 Preparation of Zn²⁺-Fixed Paclitaxel-Containing PolymericMicelles of D,L-PLA-COONa and mPEG-PLA Block Copolymer

[0161] In this example, 0.29 ml (58 mmol) of a 0.2 M anhydrous zincchloride aqueous solution was added to the polymeric micelle aqueoussolution prepared in Step 1 of the above Example 8, and the mixture wasstirred for 20 minutes at room temperature. The mixture was passedthrough a filter having a pore size of 200 nm, and then was lyophilized.

[0162] D,L-PLA-COONa/mPEG-PLA (weight ratio): 56.5/43.5

[0163] Content of paclitaxel: 11.5 wt %

[0164] Solubility of paclitaxel in the aqueous solution: 10.7 mg/ml

[0165] Particle size: 18 nm

Example 11 Preparation of Ca²⁺-Fixed Paclitaxel-Containing PolymericMicelles of D,L-PLMA-COONa and mPEG-PLA-Palmitate Block Copolymers

[0166] A Ca²⁺-fixed paclitaxel-containing polymeric micelle compositionwas prepared according to the same procedure as Example 8 except that130 mg (119 mmol) of D,L-PLMA-COONa (Mn: 1,096) of Preparation 22, 30 mgof paclitaxel, 100 mg of mPEG-PLA-Palmitate (Mn: 2,000-1,800 Daltons) ofPreparation 29, and ethanol instead of acetone were used.

[0167] D,L-PLMA-COONa/mPEG-PLA-Palmitate (weight ratio): 56.5/43.5

[0168] Content of paclitaxel: 11.5 wt %

[0169] Solubility of paclitaxel in an aqueous solution: 10.7 mg/ml

[0170] Particle size: 18 nm

Example 12 Preparation of Ca²⁺-Fixed Paclitaxel-Containing PolymericMicelles of D,L-PLA-COONa and mPEG-PLA Block Copolymers

[0171] A Ca²⁺-fixed paclitaxel-containing polymeric micelle compositionwas prepared according to the same procedure as Example 8 except that100 mg (88 mmol) of D,L-PLA-COONa (Mn: 1,140) of Preparation 13, 10 mgof paclitaxel, 90 mg of mPEG-PLA (Mn: 2,000-5,000 Daltons) ofPreparation 24, and ethanol instead of acetone were used.

[0172] D,L-PLA-COONa/mPEG-PLA (weight ratio): 54/46

[0173] Content of paclitaxel: 5.0 wt %

[0174] Solubility of paclitaxel in an aqueous solution: 10.0 mg/ml

[0175] Particle size: 58 nm

Example 13 Preparation of Ca²⁺-Fixed Paclitaxel-Containing PolymericMicelles of D,L-PLA-COONa and mPEG-PLA Block Copolymers

[0176] A Ca²⁺-fixed paclitaxel-containing polymeric micelle compositionwas prepared according to the same procedure as Example 8 except that150 mg (132 mmol) of D,L-PLA-COONa (Mn: 1,140) of Preparation 13, 10 mgof paclitaxel, 90 mg of mPEG-PLA (Mn: 2,000-8,000 Daltons) ofPreparation 25, and ethanol instead of acetone were used.

[0177] D,L-PLA-COONa/mPEG-PLA (weight ratio): 63/37

[0178] Content of paclitaxel: 4.0 wt %

[0179] Solubility of paclitaxel in an aqueous solution: 10.0 mg/ml

[0180] Particle size: 50 nm

Experimental Example 3 Evaluation of the Stability of Polymeric Micelleor Nanoparticle Compositions Depending on the Number of Equivalents of aMetal Ion used

[0181] To evaluate the stability of polymeric micelle or nanoparticlecompositions depending on the number of equivalents of metal ion used,polymeric micelle compositions were prepared as follows.

Step 1: Preparation of Paclitaxel-Containing Mixed Polymeric Micelles ofD,L-PLA-COONa and mPEG-PLA Block Copolymers

[0182] For this step, 170 mg (149 mmol) of D,L-PLA-COONa (Mn: 1,140), 30mg of paclitaxel and 50 mg of the amphiphilic block copolymer mPEG-PLA(Mn: 2,000-1,765 Daltons) were dissolved in 2 ml of acetone to obtain aclear solution. Acetone was removed therefrom to prepare apaclitaxel-containing polymeric micelle composition. Distilled water(3ml) was added to the polymeric micelle composition, and the mixture wasstirred for 30 minutes at 40° C. to prepare the paclitaxel-containingpolymeric micelle aqueous solution.

Step 2: Fixation with the Divalent Metal Ion

[0183] The paclitaxel-containing polymeric micelle aqueous solutionprepared in Step 1 was divided into 3 parts, 1 ml per part. To each partwas added 0.0625, 0.125, and 0.25 ml (12.5, 25, and 50 mmol) of a 0.2 Manhydrous calcium chloride aqueous solution. The mixture was stirred atroom temperature for 20 minutes. The mixture was passed through a filterhaving a pore size of 200 nm. Then, a phosphate buffer solution of pH7.4 was added thereto to adjust the concentration of paclitaxel to 1mg/ml. The concentration of paclitaxel was measured by HPLC whileculturing at 37° C. The results are shown in Table 8. TABLE 8 mPEG-PLA/CaCl₂/D,L- D,L-PLA-COONa PLA-COONa Drug conc. (wt. ratio) (eq.) 0 hr 6hrs 12 hrs 24 hrs 0.25 eq. 50/170 0.25/1.00 1.0 1.0 0.9 0.7 0.5 eq.50/170 0.50/1.00 1.0 1.0 1.0 1.0 1.0 eq. 50/170 1.00/1.00 1.0 1.0 1.01.0 0 eq. 50/170 0.00/1.00 1.0 0.4 0.2 0.2

[0184] As shown in Table 8, the drug concentration was reduced by 80%compared with the initial concentration and was 0.2 mg/ml after 24 hourswhen Ca²⁺ was not added. The drug concentration was reduced by about 30%compared with the initial concentration and was 0.7 mg/ml after 24 hourswhen 0.25 equivalents of Ca²⁺ was added, which was higher than that whenCa²⁺ was not added. Furthermore, the drug concentration was not changedafter 24 hours when 0.5 equivalents or more of Ca²⁺ was added. Asdescribed above, the Ca²⁺-treated composition is more stable than thenon-treated composition, and the stability was remarkably enhanced when0.5 equivalents or more of Ca²⁺ was added.

Experimental Example 4 Stability Test of the Polymeric MicellesDepending on the M.W. of the D,L-polylactic acid Sodium Salt(D,L-PLA-COONa) used

[0185] To test the stability of the nanoparticle composition dependingon the M.W. of the D,L-polylactic acid sodium salt (D,L-PLA-COONa) used,the polymeric micelle compositions were prepared as follows.

[0186] Paclitaxel, mPEG-PLA (Mn: 2,000-1,776), and D,L-PLA-COONa (Mn:646, 1,145, 1,500 or 2,300) were admixed at an equivalent ratio of1:3:3, and then the mixture was dissolved in 5 ml of anhydrous ethanolto prepare a clear solution. Ethanol was removed therefrom using vacuumevaporator to prepare a paclitaxel-containing polymeric composition.Distilled water(12 ml) was added thereto and the mixture was stirred for10 minutes at 60° C. to prepare a paclitaxel-containing polymericmicelle aqueous solution. To the above polymeric micelle solution wasadded a CaCl₂ aqueous solution (concentration: 100 mg/ml) of the samenumber of equivalents as the D,L-PLA-COONa, and the mixture was stirredfor 20 minutes at room temperature. The mixture was passed through afilter with a pore size of 200 nm, and then a phosphate buffer solutionof pH 7.4 was added thereto to dilute the mixture to have 1 mg/ml ofpaclitaxel. The mixture was allowed to stand at 37° C. and theconcentration of paclitaxel over the lapse of time was measured by HPLC.The results are shown in Table 9. TABLE 9 M.W. of Drug concentration(mg/ml) D,L-PLA-COONa 0 d 1 d 2 d 3 d 5 d 7 d 10 d 12 d 14 d 646 1.000.39 0.23 0.20 0.17 0.17 0.16 0.16 0.15 1,145 1.00 0.74 0.58 0.47 0.330.32 0.28 0.25 0.23 1,500 1.00 0.98 0.91 0.80 0.54 0.51 0.46 0.36 0.362,300 1.00 1.00 0.99 0.98 0.80 0.75 0.68 0.64 0.62

[0187] As shown in Table 9, as the M.W. of D,L-PLA-COONa was increasedto 646, 1,145, 1,500, and 2,300, the drug concentration after 14 dayswas increased to 0.15, 0.23, 0.36 and 0.62 mg/ml, respectively. As theM.W of D,L-PLA-COONa was increased, drug precipitation was decreased,which demonstrated that the polymeric micelle composition was relativelymore stabilized.

Experimental Example 5 Stability Test of the Polymeric MicellesDepending on the Number of Equivalents of D,L-polylactic acid SodiumSalt (D,L-PLA-COONa) used

[0188] To test the stability of the nanoparticle composition dependingon the number of equivalents of D,L-polylactic acid sodium salt(D,L-PLA-COONa) used, the polymeric micelle compositions were preparedas follows.

[0189] Paclitaxel, mPEG-PLA (Mn: 2,000-1,776), and D,L-PLA-COONa (Mn:646, 1,145) were admixed in an equivalent ratio of 1:2:x wherein x is 2,4, 6, 8, 10 or 12, and then the mixture was dissolved in 5 ml ofanhydrous ethanol to prepare a clear solution. Ethanol was removedtherefrom using vacuum evaporator to prepare a paclitaxel-containingpolymeric composition. Distilled water(12 ml) was added thereto and themixture was stirred for 10 minutes at 60° C. to prepare the polymericmicelle aqueous solution containing paclitaxel. To the above polymericmicelle solution was added a CaCl₂ aqueous solution (concentration: 100mg/ml) of the same number of equivalents as the D,L-PLA-COONa, and themixture was stirred for 20 minutes at room temperature. The mixture waspassed through a filter with a pore size of 200 nm, and then a phosphatebuffer solution of pH 7.4 was added thereto to dilute the mixture tohave 1 mg/ml of paclitaxel. The mixture was allowed to stand at 37° C.and the concentration of paclitaxel at different time intervals wasmeasured by HPLC. The results are shown in Table 10. TABLE 10D,L-PLA-COONa/mPEG-PLA Drug concentration (mg/ml) (eq. ratio: x/2) 0 d 1d 2 d 3 d 5 d 7 d 10 d 12 d 14 d 2/2 1.00 0.25 0.20 0.14 0.12 0.10 0.080.08 0.07 4/2 1.00 0.41 0.27 0.22 0.17 0.14 0.12 0.11 0.08 6/2 1.00 1.000.96 0.90 0.78 0.71 0.64 0.64 0.59 8/2 1.00 1.00 1.00 1.00 0.98 0.950.90 0.85 0.80 10/2  1.00 1.00 1.00 0.97 0.95 0.93 0.87 0.78 0.67 12/2 1.00 0.98 0.96 0.95 0.95 0.91 0.89 0.78 0.61

[0190] As shown in Table 10, as the number of equivalents ofD,L-PLA-COONa increased, the stability of the polymeric micelles wasincreased, and was remarkably increased at an equivalent ratio of 6/2 ormore. Particularly, the drug concentration after 14 days was a maximumof 0.80 mg/ml,, at an equivalent ratio of 8/2.

Experimental Example 6 Blood Retention Test of the Ca²⁺-FixedPaclitaxel-Containing Polymeric Micelles

[0191] To test the bloodstream retention time of Ca²⁺-fixedpaclitaxel-containing polymeric micelles, the polymeric micellecompositions were prepared as follows.

[0192] (Composition 1) Polymeric Micelles Containing Paclitaxel, a BlockCopolymer, Polylactic Acid, and a Metal Ion.

[0193] Paclitaxel, mPEG-PLA (Mn: 2,000-1,776), and D,L-PLA-COONa (Mn:1,145) were admixed at an equivalent ratio of 1:5:20, and then themixture was dissolved in 5 ml of anhydrous ethanol to prepare a clearsolution. Ethanol was removed therefrom using vacuum evaporator toprepare a paclitaxel-containing polymeric composition. Distilled water(4ml) was added thereto and the mixture was stirred for 10 minutes at 60°C. to prepare a polymeric micelle aqueous solution containingpaclitaxel. To the above polymeric micelle solution was added a CaCl₂aqueous solution (concentration: 100 mg/ml) of the same number ofequivalents as the D,L-PLA-COONa, and the mixture was stirred for 20minutes at room temperature. The mixture was passed through a filterwith a pore size of 200 nm.

[0194] (Composition 2) Mixed Polymeric Micelles Containing Paclitaxel, aBlock Copolymer, and Polylactic Acid.

[0195] Paclitaxel, MPEG-PLA (Mn: 2,000-1,776) and D,L-PLA-COONa (Mn:1,145) were admixed at an equivalent ratio of 1:5:20 and then themixture was dissolved in 5 ml of anhydrous ethanol to prepare a clearsolution. Ethanol was removed therefrom using vacuum evaporator toprepare a paclitaxel-containing polymeric composition. Distilled water(4ml) was added thereto and the mixture was stirred for 10 minutes at 60°C. to prepare a polymeric micelle aqueous solution containingpaclitaxel. The mixture was passed through a filter with a pore size of200 nm.

[0196] (Composition 3) Polymeric Micelles Containing Paclitaxel and aBlock Copolymer

[0197] Paclitaxel and mPEG-PLA (Mn: 2,000-1,776) were admixed at anequivalent ratio of 1:5 and then the mixture was dissolved in 5 ml ofanhydrous ethanol to prepare a clear solution. Ethanol was removedtherefrom using vacuum evaporator to prepare a paclitaxel-containingpolymeric composition. Distilled water(5 ml) was added thereto and themixture was stirred for 10 minutes at 60° C. to prepare a polymericmicelle aqueous solution containing paclitaxel. The mixture was passedthrough a filter with a pore size of 200 nm. TABLE 11 Content ofmPEG-PLA D,L-PLA- Paclitaxel CaCl₂ paclitaxel (mg) COONa (mg) (mg) (mg)(mg/ml) Com. 1 436.9 536.4 20.0 52.0 3.5 Com. 2 436.9 536.4 20.0 — 3.6Com. 3 436.9 — 20.0 — 3.7

[0198] For the animal experiments, male Sprague-Dawley rats of 230-250 gwere cannulated in the vena femoralis and aorta femoralis. Compositions1, 2 and 3 were injected in the vena femoralis at a dose of 10 mg/kgover 15 seconds. After injection, 0.3 ml of whole blood was taken fromthe aorta femoralis at 1, 15, 30, 45 minutes, and at 1, 1.5, 2, 3, 4, 5,6, 8 hours and then, centrifuged to obtain clear supernatant plasma.

[0199] Furthermore, to analyze the plasma concentration of drug, 0.1 mlof the plasma was introduced into a covered glass tube and 0.1 ml of anacetonitrile solution containing the internal standard substance wasadded thereto. 10 ml of ethyl acetate was added to the above solutionand the mixture was vigorously stirred for 30 seconds, and then,centrifuged at 2,500 rpm for 10 minutes. The whole ethyl acetate layerwas taken and transferred to a test tube, and then, the organic solventwas completely evaporated at 40° C. under nitrogen flow. Thereto wasadded 0.1 ml of a 40% (v/v) acetonitrile solution, and the mixture wasvigorously stirred for 30 seconds, and then, subjected to HPLC. Theconditions for HPLC were as follows:

[0200] Injection volume: 0.075 ml

[0201] Flow rate: 1.0 ml/min

[0202] Wavelength: 227 nm

[0203] Mobile phase: 24% aqueous acetonitrile solution for 5 minutes,increased to 58% for 16 minutes, increased to 70% for 2 minutes,decreased to 34% for 4 minutes, and maintained for 5 minutes

[0204] Column: 4.6×50 nm (C18, Vydac, USA).

[0205] Analysis results of the plasma concentrations of the drugs areshown in the following Table 12 and FIG. 6. TABLE 12 Plasmaconcentration of paclitaxel (μg/ml) 1 m 15 m 30 m 45 m 1 h 1.5 h 2 h 3 h4 h 5 h 6 h 8 h Com. 1 82.6 17.8 10.1 6.5 5.4 2.8 2.1 1.2 0.70 0.46 0.320.18 Com. 2 31.8 4.1 3.0 2.2 1.7 1.2 0.71 0.33 0.23 0.13 0.08 0.04 Com.3 30.4 2.4 1.6 1.1 0.90 0.66 0.39 0.17 0.09 0.07 0.03 0.02

[0206] As shown in Table 12 and FIG. 6, Composition 2 containingD,L-PLA-COONa, had a longer bloodstream retention time than Composition3 which contained mPEG-PLA block copolymer only, and Composition 1containing Ca²+had a longer retention time than Composition 2.Therefore, the above results demonstrate that the drug-containingpolymeric micelles according to the present invention had a prolongedbloodstream retention time of the drug, and particularly, the metalion-fixed polymeric micelles had a much prolonged bloodstream retentiontime of the drug.

Experimental Example 7 Bloodstream Retention Time of Ca²⁺-FixedPaclitaxel-Containing Polymeric Micelles

[0207] To compare the bloodstream retention time of the Ca²⁺-fixedpaclitaxel-containing polymeric micelles with that of formulationscontaining other carriers, the compositions were prepared as follows.

[0208] (Composition 4) Polymeric Micelles Containing Paclitaxel, a BlockCopolymer, Polylactic Acid, and a Metal Ion.

[0209] Paclitaxel, mPEG-PLA (Mn: 2,000-1,776) and D,L-PLMA-COONa (Mn:1,198) were admixed in a weight ratio of 49.5:49.5:1 and then themixture was dissolved in 5 ml of anhydrous ethanol to prepare a clearsolution. Ethanol was removed therefrom using vacuum evaporator toprepare a paclitaxel-containing polymeric composition. Distilled water(4ml) was added thereto and the mixture was stirred for 10 minutes at 60°C. to prepare a polymeric micelle aqueous solution containingpaclitaxel. To the above polymeric micelle solution was added a CaCl₂aqueous solution (concentration: 100 mg/ml) of the same number ofequivalents as the D,L-PLMA-COONa, and the mixture was stirred for 20minutes at room temperature. The mixture was passed through a filterwith a pore size of 200 nm.

[0210] (Composition 5) Composition Containing Paclitaxel, Cremophor EL,and Anhydrous Ethanol.

[0211] Paclitaxel (30 mg) was dissolved in 5 ml of a mixed solution(50:50 v/v) of Cremophor EL and anhydrous ethanol to obtain a clearsolution. The solution was passed through a filter having the pore sizeof 200 nm.

[0212] (Composition 6) Composition Containing Paclitaxel, Polysorbate 80(Tween 80), and Anhydrous Ethanol

[0213] Paclitaxel (30 mg) was dissolved in 5 ml of a mixed solution(50:50 v/v) of polysorbate 80 and anhydrous ethanol to obtain a clearsolution. The solution was passed through a filter having a pore size of200 nm.

[0214] The above composition and the drug content are summarized inTable 13. TABLE 13 Com. 4 mPEG-PLA D,L-PLMA- Paclitaxel CaCl₂ Content of(mg) COONa (mg) (mg) paclitaxel (mg) (mg/ml) 990 990 20.0 100.6 1.6 Com.5 Cremophor EL Anhydrous Paclitaxel — Content of (ml) ethanol (ml) (mg)paclitaxel (mg/ml) 2.5 2.5 30.0 — 1.5 Com. 6 Tween 80 AnhydrousPaclitaxel — Content of (ml) ethanol (ml) (mg) paclitaxel (mg/ml) 2.52.5 30.0 — 1.5

[0215] For the animal experiments, male Sprague-Dawley rats weighting230-250 g were cannulated in the vena femoralis and aorta femoralis.Compositions 4, 5 and 6 were injected into the vena femoralis at a doseof 5 mg/kg over 15 seconds. After injection, 0.3 ml of whole blood wastaken from aorta femoralis at 1, 15, 30 minutes, and at 1, 1.5, 2, 3, 4,6 hours and then, centrifuged to obtain clear supernatant plasma.

[0216] Furthermore, the plasma drug concentration was analyzed accordingto the same process as in Experimental Example 6, and the results of theplasma drug concentrations are shown in Table 14 and FIG. 7. TABLE 14Plasma concentration of paclitaxel (μg/ml) 1 m 15 m 30 m 1 h 1.5 h 2 h 3h 4 h 6 h Com. 4 86.5 9.68 4.71 1.97 1.10 0.78 0.35 0.26 0.14 Com. 545.7 6.60 3.20 1.40 0.75 0.46 0.25 0.16 0.09 Com. 6 13.9 0.64 0.26 0.100.07 0.04 — — —

[0217] As shown in Table 14 and FIG. 7, the Ca²⁺-fixed polymericmicelles (Composition 4) had a longer bloodstream retention time thanthe injections containing other surfactants (Compositions 5 and 6).Since the Ca²⁺-fixed polymeric micelles (Composition 4) of the presentinvention had a longer bloodstream retention time than the marketedformulation Taxol® (Composition 5), the present invention could increasethe drug retention time in the bloodstream over Taxol® by using thebiodegradable and biocompatible polymers.

Experimental Example 8 Anticancer Activity of Ca²⁺-FixedPaclitaxel-Containing Polymeric Micelles

[0218] A 0.1 ml of a cell suspension containing 7×10⁶ human cancer cells(PPC1, HT29) was subcutaneously injected into the sides of healthyfemale nude (nu/nu) athymic mice (20 g, 8-week aged, n=6). After thecancers reached a certain size, they were xenografted three times toform xenograft fragments of 3-4 mm. The xenograft fragments weresubcutaneously injected to the sides of healthy female nude (nu/nu)athymic mice (20 g, 8-week aged, n=5) with 12 gauge trocar needles. Whenthe volume of cancer reached 100-300 mm³, the drug was administered andthis point in time was recorded as day 0. At day 0, the mice were placedto groups of 5, and at days 0, 1, and 2, metal ion-fixed polymericmicelles (Composition 4) and the Cremophor EL formulation (Composition5) were administered at a dose of 20 mg/kg of paclitaxel through thetail vein, and the volume of the cancer were measured at different timeintervals. The volume of cancer was calculated by the formula (W²×L)/2wherein W is a short axis, and L is a long axis.

[0219] As shown in FIGS. 8a and 8 b, both the metal ion-fixed polymericmicelle-treated group and the Cremophor EL formulation-treated groupshowed a considerable inhibition on cancer growth compared with thecontrol group, and particularly, the metal ion-fixed polymericmicelle-treated group showed a higher inhibition rate than the CremophorEL formulation-treated group.

[0220] It is to be understood that the above-described embodiments areonly illustrative of the applications of the principles of the presentinvention. Numerous modifications and alternative embodiments can bederived without departing from the spirit and scope of the presentinvention and the appended claims are intended to cover suchmodifications and arrangements. Thus, while the present invention hasbeen shown in the drawings and fully described above with particularityand detail in connection with what is presently deemed to be the mostpractical and preferred embodiment(s) of the invention, it will beapparent to those of ordinary skill in the art that numerousmodifications can be made without departing from the principles andconcepts of the invention as set forth in the claims.

We claim:
 1. A polymeric composition capable of forming stable micellesin an aqueous solution, said composition comprising an amphiphilic blockcopolymer of a hydrophilic block and a hydrophobic block, and apolylactic acid derivative, wherein at least one terminal end of saidpolylactic acid derivative is covalently bound to a carboxylic acid orcarboxylate salt.
 2. The polymeric composition of claim 1, wherein theother terminal end of said polylactic acid derivative is covalentlybound to a functional group selected from the group consisting ofhydroxyl, acetoxy, benzoyloxy, decanoyloxy and palmitoyloxy groups. 3.The polymeric composition of claim 1, wherein said polylactic acidderivative is represented by the following formula:RO—CHZ-[A]_(n)-[B]_(m)-COOM   (I) wherein A is —COO—CHZ-; B is—COO—CHY—, —COO—CH₂CH₂CH₂CH₂CH₂— or —COO—CH₂CH₂OCH₂; R is a hydrogenatom, acetyl, benzoyl, decanoyl, palmitoyl, methyl or ethyl group; Z andY each are a member selected from the group consisting of a hydrogenatom, methyl, or phenyl group; M is H, Na, K, or Li; n is an integerfrom 1 to 30, and m is an integer from 0 to
 20. 4. The polymericcomposition of claim 1, wherein said polylactic acid derivative isrepresented by the following formula:RO—CHZ-[COO—CHX]_(p)—[COO—CHY′]_(q)-COO—CHZ-COOM   (II) wherein X is amethyl group; Y′ is hydrogen atom or phenyl group; p and q each are aninteger from 0 to 25 provided that p+q is an integer from 5 to 25; R isa hydrogen atom, acetyl, benzoyl, decanoyl, palmitoyl, methyl or ethylgroup; Z is a hydrogen atom, methyl, or phenyl group; and M is H, Na, K,or Li.
 5. The polymeric composition of claim 1, wherein said polylacticacid derivative is represented by the following formula:RO—PLA-COO—W-M′  (III) wherein W-M′ is

PLA is a member selected from the group consisting of D,L-polylacticacid, D-polylactic acid, polymandelic acid, a copolymer of D,L-lacticacid and glycolic acid, a copolymer of D,L-lactic acid and mandelicacid, a copolymer of D,L-Lactic acid and caprolactone, and a copolymerof D,L-lactic acid and 1,4-dioxan-2-one; R is a hydrogen atom, acetyl,benzoyl, decanoyl, palmitoyl, methyl or ethyl group; and M is H, Na, K,or Li.
 6. The polymeric composition of claim 1, wherein said polylacticacid derivative is represented by the following formula: S—O—PLA-COO-Q  (IV) wherein S is

L is —NR₁— or —O—; R₁ is a hydrogen atom or C₁₋₁₀alkyl; Q is CH₃,CH₂CH₃, CH₂CH₂CH₃, CH₂CH₂CH₂CH₃, or CH₂C₆H₅; a is an integer from 0 to4; b is an integer from 1 to 10; R is a hydrogen atom, acetyl, benzoyl,decanoyl, palmitoyl, methyl or ethyl group; M is H, Na, K, or Li and PLAis a member selected from the group consisting of D,L-polylactic acid,D-polylactic acid, polymandelic acid, a copolymer of D,L-lactic acid andglycolic acid, a copolymer of D,L-lactic acid and mandelic acid, acopolymer of D,L-Lactic acid and caprolactone, and a copolymer ofD,L-lactic acid and 1,4-dioxan-2-one.
 7. The polymeric composition ofclaim 1, wherein said hydrophilic block is a member selected from thegroup consisting of polyalkylene glycols, polyvinyl pyrrolidone,polyvinyl alcohols and polyacryl amides, and said hydrophobic block is amember selected from the group consisting of polylactides,polyglycolides, polydioxan-2-one, polycaprolactone,polylactic-co-glycolide, polylactic-co-caprolactone,polylactic-co-dioxan-2-one, and derivatives thereof.
 8. The polymericcomposition of claim 1, wherein said hydrophobic block has a carboxylterminal group which is substituted with a fatty acid group.
 9. Thepolymeric composition of claim 7, wherein the hydrophilic andhydrophobic blocks have a number average molecular weight within therange of 500 to 50,000 Daltons, respectively.
 10. The polymericcomposition of claim 1, wherein the ratio of the hydrophilic block tothe hydrophobic block in the amphiphilic block copolymer is within therange of 2:8 to 8:2.
 11. The polymeric composition of claim 1 contains 5to 95 wt % of the amphiphilic block copolymer and 5 to 95 wt % of thepolylactic acid derivative, based on the total weight of thecomposition.
 12. The polymeric composition of claim 1, wherein saidpolylactic acid derivative has a number average molecular weight of 500to 2,500 Daltons.
 13. The polymeric composition of claim 1, wherein saidpolylactic acid derivative is in a sodium or potassium salt form. 14.The polymeric composition of claim 1, further comprising 0.01 to 0.5equivalents of a di- or tri-valent metal ion with respect to 1equivalent of the carboxyl terminal group of the polylactic acidderivative.
 15. The polymeric composition of claim 14, wherein the di-or tri-valent metal ion is a member selected from the group consistingof Ca²⁺, Mg²⁺, Ba²⁺, Cr³⁺, Fe³⁺, Mn²⁺, Ni²⁺, Cu²⁺, Zn²⁺, and Al³⁺.
 16. Apharmaceutical composition capable of forming stable micelles in anaqueous solution comprising 70 to 99.9 wt % of the polymeric compositionof claim 1 and 0.1 to 30 wt % of a poorly water-soluble drug, wherein,when a micelle is formed in aqueous solution the micelle has ahydrophilic outer shell and an inner hydrophobic core, and the drug isphysically trapped within the hydrophobic core of the micelle.
 17. Ananoparticle-forming polymeric composition, comprising the polymericcomposition of claim 1, and 0.5 to 10 equivalents of the di- ortri-valent metal ion with respect to 1 equivalent of the carboxylterminal group of the polylactic acid derivative.
 18. The polymericcomposition of claim 17, wherein the di- or tri-valent metal ion is oneselected from the group consisting of Ca²⁺, Mg²⁺, Ba²⁺, Cr³⁺, Fe²⁺,Mn²⁺, Ni²⁺, Cu²⁺, Zn²⁺ and Al³⁺.
 19. A pharmaceutical compositioncomprising 70 to 99.9 wt % of the nanoparticle-forning polymericcomposition of claim 18 and 0.1 to 30 wt % of a poorly water-solubledrug.
 20. The polymeric composition of claim 3, wherein said hydrophilicblock is a member selected from the group consisting of polyalkyleneglycols, polyvinyl pyrrolidone, polyvinyl alcohols and polyacryl amides,and said hydrophobic block is a member selected from the groupconsisting of polylactides, polyglycolides, polydioxan-2-one,polycaprolactone, polylactic-co-glycolide, polylactic-co-caprolactone,polylactic-co-dioxan-2-one, and derivatives thereof.
 21. The polymericcomposition of claim 3, wherein said hydrophobic block has a carboxylterminal group which is substituted with a fatty acid group.
 22. Thepolymeric composition of claim 20, wherein the hydrophilic andhydrophobic blocks have a number average molecular weight within therange of 500 to 50,000 Daltons, respectively.
 23. The polymericcomposition of claim 3, wherein the ratio of the hydrophilic block tothe hydrophobic block in the amphiphilic block copolymer is within therange of 2:8 to 8:2.
 24. The polymeric composition of claim 3 contains 5to 95 wt % of the amphiphilic block copolymer and 5 to 95 wt % of thepolylactic acid derivative, based on the total weight of thecomposition.
 25. The polymeric composition of claim 3, wherein saidpolylactic acid derivative has a number average molecular weight of 500to 2,500 Daltons.
 26. The polymeric composition of claim 3, wherein saidpolylactic acid derivative is in a sodium or potassium salt form. 27.The polymeric composition of claim 3, further comprising 0.01 to 0.5equivalents of a di- or tri-valent metal ion with respect to 1equivalent of the carboxyl terminal group of the polylactic acidderivative.
 28. The polymeric composition of claim 27, wherein the di-or tri-valent metal ion is a member selected from the group consistingof Ca²⁺, Mg²⁺, Ba²⁺, Cr³⁺, Fe³⁺, Mn²⁺, Ni²⁺, Cu²⁺, Zn²⁺, and Al³⁺.
 29. Apharmaceutical composition capable of forming stable micelles in anaqueous solution comprising 70 to 99.9 wt % of the polymeric compositionof claim 3 and 0.1 to 30 wt % of a poorly water-soluble drug, wherein,when a micelle is formed in aqueous solution the micelle has ahydrophilic outer shell and an inner hydrophobic core, and the drug isphysically trapped within the hydrophobic core of the micelle.
 30. Ananoparticle-forming polymeric composition, comprising the polymericcomposition of claim 3, and 0.5 to 10 equivalents of the di- ortri-valent metal ion with respect to 1 equivalent of the carboxylterminal group of the polylactic acid derivative.
 31. The polymericcomposition of claim 30, wherein the di- or tri-valent metal ion is oneselected from the group consisting of Ca²⁺, Mg²⁺, Ba²⁺, Cr³⁺, Fe³⁺,Mn²⁺, Ni²⁺ and Al³⁺.
 32. A pharmaceutical composition comprising 70 to99.9 wt % of the nanoparticle-forming polymeric composition of claim 30and 0.1 to 30 wt % of a poorly water-soluble drug.
 33. The polymericcomposition of claim 4, wherein said hydrophilic block is a memberselected from the group consisting of polyalkylene glycols, polyvinylpyrrolidone, polyvinyl alcohols and polyacryl amides, and saidhydrophobic block is a member selected from the group consisting ofpolylactides, polyglycolides, polydioxan-2-one, polycaprolactone,polylactic-co-glycolide, polylactic-co-caprolactone,polylactic-co-dioxan-2-one, and derivatives thereof.
 34. The polymericcomposition of claim 4, wherein the carboxyl terminal group of saidhydrophobic block is substituted with a fatty acid group.
 35. Thepolymeric composition of claim 33, wherein the hydrophilic andhydrophobic blocks have a number average molecular weight within therange of 500 to 50,000 Daltons, respectively.
 36. The polymericcomposition of claim 4, wherein the ratio of the hydrophilic block tothe hydrophobic block in the amphiphilic block copolymer is within therange of 2:8 to 8:2.
 37. The polymeric composition of claim 4 contains 5to 95 wt % of the amphiphilic block copolymer and 5 to 95 wt % of thepolylactic acid derivative, based on the total weight of thecomposition.
 38. The polymeric composition of claim 4, wherein saidpolylactic acid derivative has a number average molecular weight of 500to 2,500 Daltons.
 39. The polymeric composition of claim 4, wherein saidpolylactic acid derivative is in a sodium or potassium salt form. 40.The polymeric composition of claim 4, further comprising 0.01 to 0.5equivalents of a di- or tri-valent metal ion with respect to 1equivalent of the carboxyl terminal group of the polylactic acidderivative.
 41. The polymeric composition of claim 40, wherein the di-or tri-valent metal ion is a member selected from the group consistingof Ca²⁺, Mg²⁺, Ba²⁺, Cr³⁺, Fe³⁺, Mn²⁺, Ni²⁺, Cu²⁺, Zn²⁺, and Al³⁺.
 42. Apharmaceutical composition capable of forming stable micelles in anaqueous solution comprising 70 to 99.9 wt % of the polymeric compositionof claim 4 and 0.1 to 30 wt % of a poorly water-soluble drug, wherein,when a micelle is formed in aqueous solution the micelle has ahydrophilic outer shell and an inner hydrophobic core, and the drug isphysically trapped within the hydrophobic core of the micelle.
 43. Ananoparticle-forming polymeric composition, comprising the polymericcomposition of claim 4 and 0.5 to 10 equivalents of the di- ortri-valent metal ion with respect to 1 equivalent of the carboxylterminal group of the polylactic acid derivative.
 44. The polymericcomposition of claim 43, wherein the di- or tri-valent metal ion is oneselected from the group consisting of Ca²⁺, Mg²⁺, Ba²⁺, Cr³⁺, Fe³⁺,Mn²⁺, Ni²⁺, Cu²⁺, Zn²⁺ and Al³⁺.
 45. A pharmaceutical compositioncomprising 70 to 99.9 wt % of the nanoparticle-forming polymericcomposition of claim 43 and 0.1 to 30 wt % of a poorly water-solubledrug.
 46. The polymeric composition of claim 5, wherein said hydrophilicblock is a member selected from the group consisting of polyalkyleneglycols, polyvinyl pyrrolidone, polyvinyl alcohols and polyacryl amides,and said hydrophobic block is a member selected from the groupconsisting of polylactides, polyglycolides, polydioxan-2-one,polycaprolactone, polylactic-co-glycolide, polylactic-co-caprolactone,polylactic-co-dioxan-2-one, and derivatives thereof.
 47. The polymericcomposition of claim 5, wherein said hydrophobic block has a carboxylterminal group which is substituted with a fatty acid group.
 48. Thepolymeric composition of claim 46, wherein the hydrophilic andhydrophobic blocks have a number average molecular weight within therange of 500 to 50,000 Daltons, respectively.
 49. The polymericcomposition of claim 5, wherein the ratio of the hydrophilic block tothe hydrophobic block in the amphiphilic block copolymer is within therange of 2:8 to 8:2.
 50. The polymeric composition of claim 5 contains 5to 95 wt % of the amphiphilic block copolymer and 5 to 95 wt % of thepolylactic acid derivative, based on the total weight of thecomposition.
 51. The polymeric composition of claim 5, wherein saidpolylactic acid derivative has a number average molecular weight of 500to 2,500 Daltons.
 52. The polymeric composition of claim 5, wherein saidpolylactic acid derivative is in a sodium or potassium salt form. 53.The polymeric composition of claim 5, further comprising 0.01 to 0.5equivalents of a di- or tri-valent metal ion with respect to 1equivalent of the carboxyl terminal group of the polylactic acidderivative.
 54. The polymeric composition of claim 53, wherein the di-or tri-valent metal ion is a member selected from the group consistingof Ca²⁺, Mg²⁺, Ba²⁺, Cr³⁺, Fe³⁺, Mn²⁺, Ni²⁺, Cu²⁺, Zn²⁺, and Al³⁺.
 55. Apharmaceutical composition capable of forming stable micelles in anaqueous solution comprising 70 to 99.9 wt % of the polymeric compositionof claim 5 and 0.1 to 30 wt % of a poorly water-soluble drug, wherein,when a micelle is formed in aqueous solution the micelle has ahydrophilic outer shell and an inner hydrophobic core, and the drug isphysically trapped within the hydrophobic core of the micelle.
 56. Ananoparticle-forming polymeric composition, comprising the polymericcomposition of claim 5, and 0.5 to 10 equivalents of the di- ortri-valent metal ion with respect to 1 equivalent of the carboxylterminal group of the polylactic acid derivative.
 57. The polymericcomposition of claim 56, wherein the di- or tri-valent metal ion is oneselected from the group consisting of Ca²⁺, Mg²⁺, Ba²⁺, Cr³⁺, Fe³⁺,Mn²⁺, Ni²⁺, Cu²⁺, Zn²⁺ and Al³⁺.
 58. A pharmaceutical compositioncomprising 70 to 99.9 wt % of the nanoparticle-forming polymericcomposition of claim 56 and 0.1 to 30 wt % of a poorly water-solubledrug.
 59. The polymeric composition of claim 6, wherein said hydrophilicblock is a member selected from the group consisting of polyalkyleneglycols, polyvinyl pyrrolidone, polyvinyl alcohols and polyacryl amides,and said hydrophobic block is a member selected from the groupconsisting of polylactides, polyglycolides, polydioxan-2-one,polycaprolactone, polylactic-co-glycolide, polylactic-co-caprolactone,polylactic-co-dioxan-2-one, and derivatives thereof.
 60. The polymericcomposition of claim 6, wherein said hydrophobic block has a carboxylterminal group which is substituted with a fatty acid group.
 61. Thepolymeric composition of claim 59, wherein the hydrophilic andhydrophobic blocks have a number average molecular weight within therange of 500 to 50,000 Daltons, respectively.
 62. The polymericcomposition of claim 6, wherein the ratio of the hydrophilic block tothe hydrophobic block in the amphiphilic block copolymer is within therange of 2:8 to 8:2.
 63. The polymeric composition of claim 6 contains 5to 95 wt % of the amphiphilic block copolymer and 5 to 95 wt % of thepolylactic acid derivative, based on the total weight of thecomposition.
 64. The polymeric composition of claim 6, wherein saidpolylactic acid derivative has a number average molecular weight of 500to 2,500 Daltons.
 65. The polymeric composition of claim 6, wherein saidpolylactic acid derivative is in a sodium or potassium salt form. 66.The polymeric composition of claim 6, further comprising 0.01 to 0.5equivalents of a di- or tri-valent metal ion with respect to 1equivalent of the carboxyl terminal group of the polylactic acidderivative.
 67. The polymeric composition of claim 66, wherein the di-or tri-valent metal ion is a member selected from the group consistingof Ca²⁺, Mg²⁺, Ba²⁺, Cr³⁺, Fe³⁺, Mn²⁺, Ni²⁺, Cu²⁺, Zn²⁺, and Al³⁺.
 68. Apharmaceutical composition capable of forming stable micelles in anaqueous solution comprising 70 to 99.9 wt % of the polymeric compositionof claim 6 and 0.1 to 30 wt % of a poorly water-soluble drug, wherein,when a micelle is formed in aqueous solution the micelle has ahydrophilic outer shell and an inner hydrophobic core, and the drug isphysically trapped within the hydrophobic core of the micelle.
 69. Ananoparticle-forming polymeric composition, comprising a polymericcomposition of claim 6 and 0.5 to 10 equivalents of the di- ortri-valent metal ion with respect to 1 equivalent of the carboxylterminal group of the polylactic acid derivative.
 70. The polymericcomposition of claim 69, wherein the di- or tri-valent metal ion is oneselected from the group consisting of Ca²⁺, Mg²⁺, Ba²⁺, Cr³⁺, Fe³⁺,Mn²⁺, Ni²⁺, Cu²⁺, Zn²⁺ and Al³⁺.
 71. A pharmaceutical compositioncomprising 70 to 99.9 wt % of the nanoparticle-forming polymericcomposition of claim 69 and 0.1 to 30 wt % of a poorly water-solubledrug.
 72. A process for preparing a pharmaceutical composition capableof forming stable micelles in an aqueous solution comprising the stepsof dissolving 70 to 99.9 wt % of the polymeric composition of claim Iand 0.1 to 30 wt % of a poorly water-soluble drug in an organic solvent,evaporating said organic solvent, and then adding an aqueous solution toform a micelle solution, wherein the micelle has a hydrophilic outershell and an inner hydrophobic core, and the drug is physically trappedwithin the hydrophobic core of the micelle with the drug beingphysically trapped within the hydrophobic core of the micelle.
 73. Theprocess of claim 72, further comprising the step of adding a di- ortri-valent metal ion to the poorly water-soluble drug-containingpolymeric micelles to fix the carboxyl terminal group of the polylacticacid derivative.
 74. The process of claim 73, wherein the di- ortri-valent metal ion is one selected from the group consisting of Ca²⁺,Mg²⁺, Ba²⁺, Cr³⁺, Fe³⁺, Mn²⁺, Ni²⁺, Cu²⁺, Zn²⁺ and Al³⁺.
 75. The processof claim 72, wherein the organic solvent is one or more selected fromthe group consisting of acetone, ethanol, methanol, ethyl acetate,acetonitrile, methylene chloride, chloroform, acetic acid, and dioxane.